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    Thread: Next Most excellent Roarkian installment:pH

    1. #1
      Bill OTMS's Avatar
      Bill OTMS is offline Most Illustrious Koi Dude
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      Next Most excellent Roarkian installment:pH

      Next Most excellent Roarkian installment:

      pH:

      To chemists, pH stands for potential of hydrogen. In simple English, pH is a measure of how acid or base the water is. The extended pH scale runs from a pH of 0.0 (strongly acid) to a pH of 14.0 (strongly base).

      You can think of the pH scale as working a bit like your cars amp-meter. When the water is perfectly balanced between acidity and baseness, the pH rests at a comfortable 7.0. As the waters acidity increases, the pH drops numerically. Conversely, as the water becomes more basic the pH increases numerically. For most koi ponds, an acceptable pH is one which lies between 6.8 and 8.6.

      The key to understanding pH rests in the notion that pH is really a measure of the number of hydrogen ions. Solutions with a high concentration of H+ ions are acidic. Solutions which are deficient of H+ ions are Basic. Hence the shorthand "pH", or "Potential Of Hydrogen".

      A quirk of the pH scale is that for each integer (whole) number of change, the actual concentration of hydrogen ions changes by a factor of ten. Thus, a change from a pH of 7.0 to 8.0 actually reflects a ten-fold increase of the base components. Looking at this another way, you could say that a ten-fold decrease in the acid component has occurred. To look at the reciprocal change, a change from a pH of 8.0 to 7.0 reflects a ten-fold increase of the acid components.

      pH can be indirectly measured using complex organic dyes whose molecular structure (and therefore color) changes predictably according to the pH. Two chemicals commonly used to measure pH are Bromothymol Blue and Cresol Red. Cresol Red is typically used for measuring pH’s between 7.4 and 8.4, while Bromothymol Blue spans the pH range of 6.5 and 7.6.

      Within these limits, the pH of an established koi pond is of little real importance. If the pH is within the range of 6.8 to 8.4 and the other water quality numbers are acceptable, koi and most plants will be happy. The key phrase here is established pond.

      In new ponds which do not have a fully cycled biofilter, the pH can become a critical issue. During the 4 to 8 week biofilter cycling process, first ammonia and then nitrites will soar to uncomfortable highs before finally coming to rest at a more comfortable trace level. In the interim, significant quantities of these compounds will be present in the water to the detriment of your fish. These compounds are highly toxic to fish and are made even more so by water with a numerically high (i.e. basic) pH. The effects of ammonia and nitrite toxicity at a pH of 8.4 are magnified by nearly a factor of 10 when compared to the effects of the same amounts at a pH of 7.2. For this reason, if you have an extremely high pH (>8.6), it may be prudent to adjust the pH toward the acid side of the spectrum prior to the initial introduction of fish. This action does not actually decrease the absolute amount of ammonia or nitrite in the water; it simply makes the resulting compounds much less toxic to fish.

      Note: Folks with bubble-bead filters beware: Reducing the pH means reducing the KH as well. BBF's *require* a KH of at least 150 ppm (175-200 ppm is better) in order to "cycle" properly. A persistent nitrite problem with a bead filter is a dead give-away you've got a KH problem.

      A ponds initial (unadjusted) pH is largely determined by the quantity and type of dissolved solids present in the water. Water with a high concentration of tannic acid (tannins), dissolved organics or sulfur compounds tends to be rather acidic. Water with a high concentration of carbonates or salts of calcium or magnesium tends toward the basic. This later condition is found predominantly in the United States but is by no means universal. Only repeated testing of your individual water source should be trusted. Note that the pH of tap water within a given municipality may vary considerably based on hourly demand or seasonal changes. In my area (Ventura, Ca.) a pH change of 0.6 points is not uncommon within just a few short hours. This occurs specifically because the delivered ratio of pumped well water (high KH) to surface water (very low KH) is varied in accordance with peak AM and PM demands.

      Copyright © 1998-2000 by Roark. All Rights Reserved.
      Email comments to: roark7@aol.com
      Page rev 1.1 of 06SEP2000

      Raising pH:

      Rising a ponds pH is frequently necessary and will at some point be required of almost every serious ponder. As nitrifying bacteria consume carbonates in their efforts to complete the Nitrification Cycle the ponds pH and Carbonate Hardness (KH) will fall. If this gradual decline is left unchecked, eventually the pond will experience a pH crash, killing fish in massive numbers and disrupting the biofilter. Periodic corrections to maintain acceptable ph / KH levels are both necessary and beneficial, especially where high stocking levels or naturally carbonate-deficient water (i.e. KH < 60ppm) is found.

      Chemical Classes
      There are two basic classes of chemicals which are used for pH control. The first and most common class consists of Carbonate-containing compounds which change the Carbonate Hardness (KH) or "KH", thereby affecting the pH indirectly. The second, rarely-used class consists of chemicals which affect the hydroxl ion concentration directly, i.e. acids and bases.

      A brief discussion of chemicals designed to raise a low pH follows:

      Sodium Bicarbonate
      Sodium bicarbonate (formula NaHCO3) is more commonly known to ponders as Arm & Hammer baking soda. Sodium bicarbonate is a supremely useful, cheap and non-toxic means of bolstering a sagging pH. It acts to raise the pH indirectly by selectively increasing the Carbonate Hardness. With a native pH of 8.4, baking soda is one of the few materials you can "eyeball" in an emergency. Once the pond hits a pH of 8.4, further additions of sodium bicarbonate will not cause the pH to raise further. Because baking soda is highly soluble, it is the tool of choice for counteracting pH crashes.

      Calcium Carbonate
      Calcium carbonate (formula CaCO3) is better known to most ponders as limestone, oyster shells etc. Calcium carbonate is a useful tool which will boost the pH indirectly by increasing the Carbonate Hardness (KH). A very useful side benefit is that CaCO3 also boosts the General Hardness (GH) by a nearly equal amount. If you live in an area which experiences heavy rainfall or where the ground water is calcium poor, CaCO3 can be used to great effect. The only drawback to using CaCO3 is the time required for it to dissolve. You are literally dissolving a rock. Depending on the temperature and pH of your water, it can take weeks or months for a handful of calcium carbonate to dissolve. For fast pH or KH corrections, look to another compound.

      Sodium Carbonate
      A close cousin to both calcium carbonate and sodium bicarbonate, sodium carbonate has a native pH of about 8.8 and can be used in a manner similar to baking soda. It too selectively bolsters the carbonate hardness (KH) without changing to the General Hardness (GH). The pH increase occurs indirectly as a result of increasing the KH. Like baking soda, it dissolves very quickly and is non-toxic to fish.

      Sodium Hydroxide
      Better known as household lye (the active ingredient in caustic drain openers such as "Draino"), sodium hydroxide (formula NaOH) is some mean stuff and is best left to very advanced ponders. Unlike all the preceding compounds I've mentioned, sodium hydroxide manipulates the pH directly via the addition of large amounts of OH ions. Sodium hydroxide has a native pH of 13+, so use must be in very small, controlled amounts. Like muriatic acid, NaOH can drop the floor right out of your carbonate buffers. (This statement seems counter-intuitive unless you call that carbonates attempt to buffer against pH changes. Carbonates are consumed equally regardless if they are resisting a change toward the acidic or basic end of the pH scale.) I've included this compound because it is occasionally useful when weird water chemistry prevails or a fast rise in pH is needed beyond the ability of other, safer, compounds. Sodium hydroxide is generally shipped as a granular white powder which is highly soluble in water. If you leave the lid off a jar of NaOH, it will quickly turn into a goopy mess as it grabs moisture from the air. Even though it is technically not an acid, use the same acid safety guidelines for safe storage and handling.

      Calcium Hydroxide
      Known to builders and gardeners as "slaked lime", calcium hydroxide (formula Ca (OH) 2 is a grayish powder which has an effect similar to Sodium Hydroxide. Because this compound also serves to increase the General Hardness (GH), it is sometimes used to pre-correct very acid, calcium-poor water. Like NaOH, it too manipulates the pH directly via the addition of OH ions. Similarly, it can crash a ponds Carbonate Hardness (KH) if used recklessly. This compound is best left to advance ponders.

      Copyright © 1998-2000 by Roark. All Rights Reserved.
      Email comments to: roark7@aol.com
      Page rev 1.1 of 01SEP2000

      Muriatic Acid Is Highly Toxic To Fish
      Nope. Muriatic acid (aka hydrochloric acid, hydrogen chloride, "Pool acid") is *harmless* to koi and goldfish when used responsibly. In fact, HCl is the correct tool for the job if you live in a hard-water area (like me!). Very little HCl is needed, it is non-toxic when dispersed in water, does not introduce food for bacteria, and is *dirt* cheap. See the discussion on Reducing Carbonate Hardness before using it however. Like any strong acid, it can drop the floor right out of KH figure right in a big hurry. But note this isn't "toxicity". Far from it. Any acidic compound will do this. HCL just excels at it far above what would seem to be a "normal" level. Lacking any carbonate buffers, adding HCl *will* produce a pH crash and this *will* kill fish. Acid is a tool. Use it wisely.

      Use Vinegar To Safely Lower A Ponds pH - Nope
      I used to encounter this all the time in rec. ponds. Every now and then I still get mail on the subject. For the record, vinegar is acetic acid with a concentration of 3% to 6%. Acetic acid is a very poor, very weak, complex, organic acid. It makes great salad dressing but a lousy acid. When compared to simple 2-element acids (i.e. HCl), acetic acid has only one free hydrogen to contribute for every 100-ish atoms. In contrast, hydrochloric acid has one free hydrogen per molecule when it dissociates in water. Want to hear a kicker? Acetic acid is actually toxic to fish. No kidding. To further add insult to injury, vinegar decomposes into a long list of organic, all of which must be broken-down by bacterial action. This increases the bioload on your pond, consumes oxygen, and contributes to high waterborne bacterial counts. Vinegar in solution is an eye and gill irritant as well. With all these problems, you wonder why people continue to use it.
      Note: I once did a math comparison between HCl and Vinegar. Did you know it would take over two *gallons* of evil-smelling vinegar to equal the acidification power of 50 cc's of HCl?



      pH Crash!

      Description
      A very sudden, unusually low pH reading generally occurring overnight or in the late afternoon is called a "pH Crash". Don't confuse this with the normal morning-afternoon-evening fluctuations (typically a maximum of 0.4 points). A crash is permanent pH nose-dive toward the acid end of the scale. In a heavily stocked pond, it can happen very fast. Generally, crashes are more prevalent during the summer months when the fish are eating well, the water is warm, and biofilter activity is high. pH crash is capable of killing fish in large numbers. Left to itself the situation will not magically get better. It will get worse. Much worse. Treatment must be immediate and aggressive or you WILL LOSE FISH.

      What Causes It
      A pH crash occurs when carbonate buffers (KH) are severely depleted by normal biological action. A pH crash can also be caused by improper addition of an acid or a sudden, massive influx of non-carbonate containing water (i.e., rainfall or surface runoff).

      Symptoms
      Fish roll-over, gasp, swim erratically, appear dazed, sit on the bottom, wont eat, or are just plain dead. Water may look hazy or smell "fishy". Some fish may excrete large amounts of slime and have frayed fins.

      Confirming Evidence
      If you suspect a pH crash, it is a simple matter to confirm it, as follows:

      Step #1: Measure your pH
      • If the pH is under your "normal-low" reading by more than 0.5 point, it is highly likely you have a pending pH crash.
      • If your pH is under 6.0, you have a confirmed pH crash.
      Step #2: Measure your Carbonate Hardness (KH)
      • If the KH (carbonate hardness) is under 80 ppm but above 40 ppm, you have a pending pH crash. This condition will develop into a full-blown crash if not treated immediately.
      • If the KH is under 40, you have a confirmed pH crash.
      Step #3: Test For Ammonia
      • If ammonia is not detected, or is detected only in very small (trace) amounts, preceded as directed under "Corrective Actions", as appropriate for your type of crash.
      • If ammonia is detected, you have a very serious problem. Raising the pH will reverse the pH shock, but will likely kill the surviving fish by ammonia poisoning. (Remember that ammonia becomes more toxic to fish as the pH increases toward the alkaline end of the pH scale.) Go to the "Corrective Actions" section titled "Crash With Ammonia Present"
      Corrective Actions
      So we've confirmed we have a problem? Major bummer, dude. Fortunately, correction of the problem is as close as the baking section of your local grocery store.

      Confirmed pH Crash
      Move quickly. Add sodium bicarbonate (unscented household baking soda) at the rate of 1 cup per 500 gallons. Add this dose to a 5 gallon bucket of pond water. Stir well until the water is clear (about 2 minutes). Distribute this mixture evenly around the pond. If you have spray bars, run them to mix the solution into the water. Remeasure the pH and hardness in 15-20 minutes. Subsequent doses at the rate of 1 cup per 500 gallons may be needed to pull the pH and KH back up to a reasonable level (i.e., pH >7.4 and KH in the range of 80 to 120 ppm).

      Pending pH Crash
      Add sodium bicarbonate (unscented household baking soda) at the rate of 1 cup per 1000 gallons. Add this dose to a 5 gallon bucket of pond water. Stir well until the water is clear (about 2 minutes). Distribute this mixture evenly around the pond. If you have spray bars, run them to mix the solution into the water. Subsequent doses at the rate of 1 cup per 1000 gallons may be needed to pull the pH and KH back up to a reasonable level (i.e., pH >7.4 and KH in the range of 80 to 120 ppm).

      Crash With Ammonia
      Special precautions need to be taken when ammonia is present due to its increasing toxicity with increasing pH. Unlike crashes where ammonia is not detected, recovery needs to be carefully executed to avoid killing your fish. The idea is to bring the pH up far enough to comfortably support life while at the same time minimizing ammonia toxicity. The following procedure also adds supplemental oxygen since ammonia affects the fish’s ability to breathe. Do the following procedure in order and exactly as written.

      Dose the pond with AmQuel at one and one-half times (150%) the manufacturers recommended label dosage. (If you've got spraybars run them at full-throttle and the outlook for your fish will be vastly improved.) Wait 5 minutes. Add drugstore-strength hydrogen peroxide (3% solution) at the rate of 0.25 to 0.5 cc/gallon. Wait a minute or two for the H2O2 to disperse throughout the pond. Add sodium bicarbonate (unscented household baking soda) at the rate of 1 cup per 1000 gallons. Add this dose to a 5 gallon bucket of pond water. Stir well until the water is clear (about 2 minutes) then distribute this mixture evenly around the pond. Wait five minutes, and then retest the pH. If the pH is still below 7.4, add additional sodium bicarbonate at the rate of 1 cup per 5000 gallons. Successive doses at this level may be made to achieve a 7.4 pH as long as sufficient time is allowed for the previous dose to become uniformly distributed (this prevents a pH test from misreading due to a locally high/low concentration of sodium bicarbonate).

      If you have the means to perform a partial water change, consider doing it. In instances where a high ammonia concentration is measured, this is a must. Fish which have been pH shocked and ammonia-tox'ed have a very poor outlook. Reducing the ammonia level by dilution after correcting the pH crash is an excellent strategy.

      Follow-Up For Non-Ammonia Types Of Crash
      Continue aeration for 24 hours. Once the pH has risen sufficiently and appears stable, re-measure the pH and KH in 12 hours and adjust either/both in the upward direction only as needed. Don't be surprised if your pH jumps to 8.0 or 8.2. Koi are perfectly happy at these levels. Feed very sparingly for the next week. Measure your pH, KH, and Ammonia levels daily for the next several weeks. Stop feeding immediately if any ammonia is detected. Monitor nitrite levels weekly for the next 2 months.

      Follow-Up For Crashes Where Ammonia Is Present
      Continue heavy aeration for 24-48 hours. Spraybars are ideal for this type of long-term support. Once the pH has risen into the low to mid-7, re-measure the pH and KH in 12 hours and resist further adjustments in any direction until the ammonia level drops to zero. If the pH swings over 7.4 to 7.6, redose the pond with AmQuel at half the label dose and begin a series of partial water changes (20%). Don't be surprised if you detect nitrites in the following two weeks. Biofilters can be severely damaged by the low pH levels encountered in a hard crash. Feed very sparingly (preferably don't feed at all) for the next week. Measure your pH, KH, and Ammonia levels daily for the next several weeks. Monitor nitrite levels weekly for the next 2 months. Carefully inspect your fish for signs of opportunistic disease.



      A Word About Sudden pH Changes
      Having just forced your pH to jump from sub-6 into the low-8's, you are likely to recall someone saying that *any* pH change greater than 0.2 pH points per day is bad for the fish. The truth is this: Any pH change is certainly stressful to some degree, but a sudden change toward the basic (i.e., numerically greater) end of the pH scale is tolerated fairly well by koi. It is sudden changes toward the acid end of the scale which typically kill fish in large numbers. I'll grant you that the huge upward change you just made is far from optimal, but recall that in a crashed pond, everything will be dead within just a few hours anyway. This adjustment was done as an emergency action and is a calculated risk. As long as you don't make a habit of these sudden adjustments, your fish should be fine.

      Prevention Of Future Crashes
      There is only *one* reason a pH crash ever occurs. Take a good look in the mirror and know your enemy. A pH crash is impossible in a pond where the proper carbonate hardness (KH) is maintained. Read that line again. It’s important. Ponds don't just "crash" unless they are seriously neglected. By maintaining your KH in the 80 to 120 ppm region, you'll never see another pH crash. Purchase a good pH / KH test kit and learn how to use it. Measure the pH and KH parameters weekly during the summer months and monthly in the winter months. Record your results. If needed, support the ponds carbonate level by periodic additions of small amounts of sodium bicarbonate or powdered limestone. Don't wait until your buffers are severely depleted to supplement your KH.


      Copyright © 1998 by Roark. All Rights Reserved.
      Email comments to: roark7@aol.com
      Page rev 7.12 of 06FEB98

      Batmasters aka Phil pointed out a great exchange:

      Batmasters 08-03-2007 09:16 AM

      Understanding pH and crashes-Help

      I just finished reading the sub-forum on water quality and found it really informative. Either I missed it, or it is not there, but what I'm trying to understand is why a pH crash occurs. The thread explains very well how it happens, and what to do, but not why. As I understand it, a crash occurs in a pond with low KH. According to the thread, it doesn't have to be ammonia or nitrite because they could be low as well. That being the case, what triggers a crash? The acid has to come from somewhere to cause the pH to drop doesn't it?

      I have low KH in my pond, but have never had a measurement of any ammonia or nitrite other than 0. Do I really have to worry about a crash as long as that remains true? Under what circumstances, other than ammonia and nitrite spiking, could the pH crash?

      Phil

      cppond 08-03-2007 09:39 AM

      Part of the nitrification cycle "consumes" kh. Therefore, the process reduces, and theoretically can deplete your kh. One school of thought is to keep the kh high in order to avoid that using BS, for instance. Another school of thought states that, presuming your source water has even moderate kh, regular water changes will replenish the kh and avoid a crash.



      Batmasters 08-03-2007 09:47 AM

      We have our wonderful Rocky Mountain water, almost no hardness. When I measured our tap water it was one drop for KH and 4 for GH. I'm aware of adding BS. If nitrification consumes KH, when KH was gone nitrite and ammonia would be over 0. Since I don't see that, then the KH is maintaining itself, just at a low level.


      Cowiche Ponder 08-03-2007 09:57 AM

      A large amount of rain can add the acid to the pond that can cause a crash. Seems that is what I read the most as a cause.


      cppond 08-03-2007 10:04 AM

      Your pond may never crash at a low ph if there is never an increased demand on the system. However, theoretically, something could occur to cause an increased demand, such as a spawn, etc.



      Batmasters 08-03-2007 11:47 AM
      *
      That's what I'm looking for, spawning and heavy rain are two possible causes. I'm guessing that increased fish load or fish growing might also cause problems in terms of stressing filters, but they would be slow or fairly predictable. Anything else?



      Brutuscz 08-03-2007 12:00 PM

      I had a ph crash 2 weeks ago in my indoor holding tank. My gh is 40-60 and kh 20-30 usually and tds=50. I noticed the fish had turned glowing red, and looked awful overnight. My ph test kit goes down to 6.2 and that's what it showed. Was probably way lower. All the fish died in that tank. In my own pond, I have 80lbs of calcite sand in the filter and add baking soda regularly. I just never considered it in my holding tank. Live and learn!!


      Batmasters 08-03-2007 12:18 PM

      I'm sorry for the loss of your fish. Any idea what changed, if anything? I'm really trying to get to the heart of this issue with this thread, not just for me, but for general information for all. My pond numbers are not much different than your indoor tank, a little higher but not much.My QT numbers are lower! I'm looking for long-term ways of changing hardness; the idea of adding BS weekly isn't appealing but I'll do it if I must to maintain the health of the fish.

      Phil



      Joey S 08-03-2007 12:21 PM

      Here's a good explanation of the chemical forces at work from Doc Johnson. http://www.koivet.com/html/articles/...article_id=206



      IMSALSMOM 08-03-2007 12:26 PM

      http://www.koivet.com/html/articles/...ater%20Quality

      I USE OYSTER SHELL. IT WORKS FOR ME, MY KH STAYS ABOUT 180.



      Graham 08-03-2007 01:41 PM

      Oyster shell is not capable of dissolving fast enough to prevent a PH crash. Heavy acidic rains can drp pH a like a rock and the shell would be playing catch up.

      KH is a constantly dropping number as every biological process in the pond is using it and then on a nightly basis the formation of carbonic acid drops it but gives it back during the day.

      So while 50ppm might be fine in a pond with very little algae or plants : one with green water could crash it out

      G


      Roddy Conrad 08-03-2007 10:10 PM

      When we feed our koi, the wastes create ammonia which has to be bioconverted since the ammonia is toxic to the koi. The biofiltration process of ammonia conversion consumes alkalinity by producing acid. So unless there is a constant addition to the pond of some form of alkalinity, the acid produced from feeding the koi will eventually consume the available alkalinity to give pH crash and loss of the biofiltration function. This will kill the fish if not corrected soon enough. No backyard fish pond can ever become “permanently balanced” without refreshing the alkalinity by water exchange, or baking soda addition, or other forms of alkalinity addition. Each pound of koi pellets added to the pond water causes the biofiltration to consume a half pound of baking soda equivalence in pond water alkalinity. In my own ponds, for each 25 pound bag of koi food used, I dump in a 12 pound bag of baking soda to maintain the alkalinity for the biofiltration to keep the water parameters optimized. For those lucky enough to have water supplies that contain reasonable levels of alkalinity, water exchange can provide the needed alkalinity refreshment. But if your water supply has low or no alkalinity, like my supply water, adding baking soda for alkalinity and pH control is the most practical approach. When the water source is above 100 ppm in alkalinity, water change is the usual preferred practice of alkalinity maintenance, but when the water source is below 80 ppm alkalinity, the addition of baking soda is usually required to avoid pH crash and to avoid pH variation.

      A pound of baking soda added per 1000 USA gallons increases the alkalinity by 71 ppm. Baking soda is pure sodium bicarbonate, available at your local grocery store for typically 40 cents per pound. I buy 12 pound bags of baking soda at the local Sam’s, since that is a more convenient quantity for our pond use. For most koi ponds, 80 ppm alkalinity is the minimum safe level to avoid pH crash for a reasonable time before checking the value with the next measurement. In koi ponds with higher stocking densities and feed rates (meaning mine, for example), higher alkalinity values are desirable for a safer alkalinity cushion to avoid pH crash and loss of biofiltration. The conversion of ammonia stops in the pH range of 6 to 6.5, since there is no longer any alkalinity to consume the acid produced by ammonia conversion. In my own koi ponds at their heavy stocking level, I prefer to maintain the alkalinity in the 150 to 500 ppm range with baking soda addition since the alkalinity drops 15 to 25 ppm per day at high koi stocking levels and high feed rates during summer months. If I tried to run alkalinity values below 100 ppm, or pH values below 7.8, I would have to add baking soda daily in my own ponds to avoid large pH variation and water quality problems that cause fish health issues. At the higher alkalinity values, the addition of baking soda is only needed once every two weeks.

      The ammonia in the pond water is much more toxic to the koi at higher pH values since more of the ammonia is in the unionized toxic form at higher pH values. So when the alkalinity is going to be increased by either water exchange or baking soda addition, the ammonia level needs to be checked until you are sure the filter is adequately converting the ammonia routinely. If the ammonia has built up to significant levels, meaning 2 ppm or higher, the safest practice is to chemically bind the ammonia with Amquel or ChlorAmX before making alkalinity and pH adjustment by either baking soda addition or water exchange.

      The biofiltration process performs better when the pH is in the 7.8 to 8.5 range, and the alkalinity is in the 100 to 500 ppm range. For instance, the basic research at Louisiana State University on the use of bead filters for intensive fish culture reported a minimum alkalinity requirement of 150 ppm for adequate performance of bead filters for conversion of ammonia and nitrite at high fish loads. All filtration systems are more efficient to bioconvert ammonia and nitrite at higher alkalinity and pH values, but many well aerated biofilter designs work well enough at alkalinities below the minimum 150 ppm value required for adequate bead filter bioconversion efficiency.

      There are two major requirements for the pH value of the water in a koi pond. The first requirement is that the pH be above a value of 7 to provide alkalinity for bioconversion as discussed above, since bioconversion consumes alkalinity and causes pH crash. The second requirement is pH value stability, since rapid variation in pH can stress the koi and cause both health problems and coloration loss. Higher alkalinity gives more stability to the pH value, and is healthier for the koi. The upper limit of good pH values for koi keeping is a value of 9, and the preferable range is 7.8 to 8.4, where biofiltration is at its maximum efficiency.

      Algae and other plant life in koi ponds can destabilize the pH of the water by producing carbon dioxide at night to give low pH at sunrise, and consume carbon dioxide in the day to give relatively high pH at the sunset. Higher alkalinity stabilizes this pH cycle.



      Batmasters 08-03-2007 10:27 PM

      Roddy,

      That is a great explanation and makes perfect sense. What I didn't realize is that the conversion of ammonia takes KH and thus the KH needs to be replenished simply because the fish are present. My water is very soft--so water changes won't make up the difference. I guess I buy stock in Arm & Hammer and go to adding it regularly. I like the idea of keeping it high so it is only necessary to add it every couple of weeks.

      My quest for trigger mechanisms is answered by this. There isn't one, simply the day to day operation of the pond, fish, and food can trigger a pH crash plus the rain and spawning as unusual triggers.

      Thanks
      Phil
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      Bill OTMS;1039030]Next Most excellent Roarkian installment:

      pH:

      To chemists, pH stands for potential of hydrogen. In simple English, pH is a measure of how acid or base the water is. The extended pH scale runs from a pH of 0.0 (strongly acid) to a pH of 14.0 (strongly base).

      You can think of the pH scale as working a bit like your cars amp-meter. When the water is perfectly balanced between acidity and baseness, the pH rests at a comfortable 7.0. As the waters acidity increases, the pH drops numerically. Conversely, as the water becomes more basic the pH increases numerically. For most koi ponds, an acceptable pH is one which lies between 6.8 and 8.6.

      The key to understanding pH rests in the notion that pH is really a measure of the number of hydrogen ions. Solutions with a high concentration of H+ ions are acidic. Solutions which are deficient of H+ ions are Basic. Hence the shorthand "pH", or "Potential Of Hydrogen".

      A quirk of the pH scale is that for each integer (whole) number of change, the actual concentration of hydrogen ions changes by a factor of ten. Thus, a change from a pH of 7.0 to 8.0 actually reflects a ten-fold increase of the base components. Looking at this another way, you could say that a ten-fold decrease in the acid component has occurred. To look at the reciprocal change, a change from a pH of 8.0 to 7.0 reflects a ten-fold increase of the acid components.

      pH can be indirectly measured using complex organic dyes whose molecular structure (and therefore color) changes predictably according to the pH. Two chemicals commonly used to measure pH are Bromothymol Blue and Cresol Red. Cresol Red is typically used for measuring pH’s between 7.4 and 8.4, while Bromothymol Blue spans the pH range of 6.5 and 7.6.

      Within these limits, the pH of an established koi pond is of little real importance. If the pH is within the range of 6.8 to 8.4 and the other water quality numbers are acceptable, koi and most plants will be happy. The key phrase here is established pond.

      In new ponds which do not have a fully cycled biofilter, the pH can become a critical issue. During the 4 to 8 week biofilter cycling process, first ammonia and then nitrites will soar to uncomfortable highs before finally coming to rest at a more comfortable trace level. In the interim, significant quantities of these compounds will be present in the water to the detriment of your fish. These compounds are highly toxic to fish and are made even more so by water with a numerically high (i.e. basic) pH. The effects of ammonia and nitrite toxicity at a pH of 8.4 are magnified by nearly a factor of 10 when compared to the effects of the same amounts at a pH of 7.2. For this reason, if you have an extremely high pH (>8.6), it may be prudent to adjust the pH toward the acid side of the spectrum prior to the initial introduction of fish. This action does not actually decrease the absolute amount of ammonia or nitrite in the water; it simply makes the resulting compounds much less toxic to fish.

      Note: Folks with bubble-bead filters beware: Reducing the pH means reducing the KH as well. BBF's *require* a KH of at least 150 ppm (175-200 ppm is better) in order to "cycle" properly. A persistent nitrite problem with a bead filter is a dead give-away you've got a KH problem.

      A ponds initial (unadjusted) pH is largely determined by the quantity and type of dissolved solids present in the water. Water with a high concentration of tannic acid (tannins), dissolved organics or sulfur compounds tends to be rather acidic. Water with a high concentration of carbonates or salts of calcium or magnesium tends toward the basic. This later condition is found predominantly in the United States but is by no means universal. Only repeated testing of your individual water source should be trusted. Note that the pH of tap water within a given municipality may vary considerably based on hourly demand or seasonal changes. In my area (Ventura, Ca.) a pH change of 0.6 points is not uncommon within just a few short hours. This occurs specifically because the delivered ratio of pumped well water (high KH) to surface water (very low KH) is varied in accordance with peak AM and PM demands.

      Copyright © 1998-2000 by Roark. All Rights Reserved.
      Email comments to: roark7@aol.com
      Page rev 1.1 of 06SEP2000

      Raising pH:

      Rising a ponds pH is frequently necessary and will at some point be required of almost every serious ponder. As nitrifying bacteria consume carbonates in their efforts to complete the Nitrification Cycle the ponds pH and Carbonate Hardness (KH) will fall. If this gradual decline is left unchecked, eventually the pond will experience a pH crash, killing fish in massive numbers and disrupting the biofilter. Periodic corrections to maintain acceptable ph / KH levels are both necessary and beneficial, especially where high stocking levels or naturally carbonate-deficient water (i.e. KH < 60ppm) is found.

      Chemical Classes
      There are two basic classes of chemicals which are used for pH control. The first and most common class consists of Carbonate-containing compounds which change the Carbonate Hardness (KH) or "KH", thereby affecting the pH indirectly. The second, rarely-used class consists of chemicals which affect the hydroxl ion concentration directly, i.e. acids and bases.

      A brief discussion of chemicals designed to raise a low pH follows:

      Sodium Bicarbonate
      Sodium bicarbonate (formula NaHCO3) is more commonly known to ponders as Arm & Hammer baking soda. Sodium bicarbonate is a supremely useful, cheap and non-toxic means of bolstering a sagging pH. It acts to raise the pH indirectly by selectively increasing the Carbonate Hardness. With a native pH of 8.4, baking soda is one of the few materials you can "eyeball" in an emergency. Once the pond hits a pH of 8.4, further additions of sodium bicarbonate will not cause the pH to raise further. Because baking soda is highly soluble, it is the tool of choice for counteracting pH crashes.

      Calcium Carbonate
      Calcium carbonate (formula CaCO3) is better known to most ponders as limestone, oyster shells etc. Calcium carbonate is a useful tool which will boost the pH indirectly by increasing the Carbonate Hardness (KH). A very useful side benefit is that CaCO3 also boosts the General Hardness (GH) by a nearly equal amount. If you live in an area which experiences heavy rainfall or where the ground water is calcium poor, CaCO3 can be used to great effect. The only drawback to using CaCO3 is the time required for it to dissolve. You are literally dissolving a rock. Depending on the temperature and pH of your water, it can take weeks or months for a handful of calcium carbonate to dissolve. For fast pH or KH corrections, look to another compound.

      Sodium Carbonate
      A close cousin to both calcium carbonate and sodium bicarbonate, sodium carbonate has a native pH of about 8.8 and can be used in a manner similar to baking soda. It too selectively bolsters the carbonate hardness (KH) without changing to the General Hardness (GH). The pH increase occurs indirectly as a result of increasing the KH. Like baking soda, it dissolves very quickly and is non-toxic to fish.

      Sodium Hydroxide
      Better known as household lye (the active ingredient in caustic drain openers such as "Draino"), sodium hydroxide (formula NaOH) is some mean stuff and is best left to very advanced ponders. Unlike all the preceding compounds I've mentioned, sodium hydroxide manipulates the pH directly via the addition of large amounts of OH ions. Sodium hydroxide has a native pH of 13+, so use must be in very small, controlled amounts. Like muriatic acid, NaOH can drop the floor right out of your carbonate buffers. (This statement seems counter-intuitive unless you call that carbonates attempt to buffer against pH changes. Carbonates are consumed equally regardless if they are resisting a change toward the acidic or basic end of the pH scale.) I've included this compound because it is occasionally useful when weird water chemistry prevails or a fast rise in pH is needed beyond the ability of other, safer, compounds. Sodium hydroxide is generally shipped as a granular white powder which is highly soluble in water. If you leave the lid off a jar of NaOH, it will quickly turn into a goopy mess as it grabs moisture from the air. Even though it is technically not an acid, use the same acid safety guidelines for safe storage and handling.

      Calcium Hydroxide
      Known to builders and gardeners as "slaked lime", calcium hydroxide (formula Ca (OH) 2 is a grayish powder which has an effect similar to Sodium Hydroxide. Because this compound also serves to increase the General Hardness (GH), it is sometimes used to pre-correct very acid, calcium-poor water. Like NaOH, it too manipulates the pH directly via the addition of OH ions. Similarly, it can crash a ponds Carbonate Hardness (KH) if used recklessly. This compound is best left to advance ponders.

      Copyright © 1998-2000 by Roark. All Rights Reserved.
      Email comments to: roark7@aol.com
      Page rev 1.1 of 01SEP2000

      Muriatic Acid Is Highly Toxic To Fish
      Nope. Muriatic acid (aka hydrochloric acid, hydrogen chloride, "Pool acid") is *harmless* to koi and goldfish when used responsibly. In fact, HCl is the correct tool for the job if you live in a hard-water area (like me!). Very little HCl is needed, it is non-toxic when dispersed in water, does not introduce food for bacteria, and is *dirt* cheap. See the discussion on Reducing Carbonate Hardness before using it however. Like any strong acid, it can drop the floor right out of KH figure right in a big hurry. But note this isn't "toxicity". Far from it. Any acidic compound will do this. HCL just excels at it far above what would seem to be a "normal" level. Lacking any carbonate buffers, adding HCl *will* produce a pH crash and this *will* kill fish. Acid is a tool. Use it wisely.

      Use Vinegar To Safely Lower A Ponds pH - Nope
      I used to encounter this all the time in rec. ponds. Every now and then I still get mail on the subject. For the record, vinegar is acetic acid with a concentration of 3% to 6%. Acetic acid is a very poor, very weak, complex, organic acid. It makes great salad dressing but a lousy acid. When compared to simple 2-element acids (i.e. HCl), acetic acid has only one free hydrogen to contribute for every 100-ish atoms. In contrast, hydrochloric acid has one free hydrogen per molecule when it dissociates in water. Want to hear a kicker? Acetic acid is actually toxic to fish. No kidding. To further add insult to injury, vinegar decomposes into a long list of organic, all of which must be broken-down by bacterial action. This increases the bioload on your pond, consumes oxygen, and contributes to high waterborne bacterial counts. Vinegar in solution is an eye and gill irritant as well. With all these problems, you wonder why people continue to use it.
      Note: I once did a math comparison between HCl and Vinegar. Did you know it would take over two *gallons* of evil-smelling vinegar to equal the acidification power of 50 cc's of HCl?



      pH Crash!

      Description
      A very sudden, unusually low pH reading generally occurring overnight or in the late afternoon is called a "pH Crash". Don't confuse this with the normal morning-afternoon-evening fluctuations (typically a maximum of 0.4 points). A crash is permanent pH nose-dive toward the acid end of the scale. In a heavily stocked pond, it can happen very fast. Generally, crashes are more prevalent during the summer months when the fish are eating well, the water is warm, and biofilter activity is high. pH crash is capable of killing fish in large numbers. Left to itself the situation will not magically get better. It will get worse. Much worse. Treatment must be immediate and aggressive or you WILL LOSE FISH.

      What Causes It
      A pH crash occurs when carbonate buffers (KH) are severely depleted by normal biological action. A pH crash can also be caused by improper addition of an acid or a sudden, massive influx of non-carbonate containing water (i.e., rainfall or surface runoff).

      Symptoms
      Fish roll-over, gasp, swim erratically, appear dazed, sit on the bottom, wont eat, or are just plain dead. Water may look hazy or smell "fishy". Some fish may excrete large amounts of slime and have frayed fins.

      Confirming Evidence
      If you suspect a pH crash, it is a simple matter to confirm it, as follows:

      Step #1: Measure your pH
      • If the pH is under your "normal-low" reading by more than 0.5 point, it is highly likely you have a pending pH crash.
      • If your pH is under 6.0, you have a confirmed pH crash.
      Step #2: Measure your Carbonate Hardness (KH)
      • If the KH (carbonate hardness) is under 80 ppm but above 40 ppm, you have a pending pH crash. This condition will develop into a full-blown crash if not treated immediately.
      • If the KH is under 40, you have a confirmed pH crash.
      Step #3: Test For Ammonia
      • If ammonia is not detected, or is detected only in very small (trace) amounts, preceded as directed under "Corrective Actions", as appropriate for your type of crash.
      • If ammonia is detected, you have a very serious problem. Raising the pH will reverse the pH shock, but will likely kill the surviving fish by ammonia poisoning. (Remember that ammonia becomes more toxic to fish as the pH increases toward the alkaline end of the pH scale.) Go to the "Corrective Actions" section titled "Crash With Ammonia Present"
      Corrective Actions
      So we've confirmed we have a problem? Major bummer, dude. Fortunately, correction of the problem is as close as the baking section of your local grocery store.

      Confirmed pH Crash
      Move quickly. Add sodium bicarbonate (unscented household baking soda) at the rate of 1 cup per 500 gallons. Add this dose to a 5 gallon bucket of pond water. Stir well until the water is clear (about 2 minutes). Distribute this mixture evenly around the pond. If you have spray bars, run them to mix the solution into the water. Remeasure the pH and hardness in 15-20 minutes. Subsequent doses at the rate of 1 cup per 500 gallons may be needed to pull the pH and KH back up to a reasonable level (i.e., pH >7.4 and KH in the range of 80 to 120 ppm).

      Pending pH Crash
      Add sodium bicarbonate (unscented household baking soda) at the rate of 1 cup per 1000 gallons. Add this dose to a 5 gallon bucket of pond water. Stir well until the water is clear (about 2 minutes). Distribute this mixture evenly around the pond. If you have spray bars, run them to mix the solution into the water. Subsequent doses at the rate of 1 cup per 1000 gallons may be needed to pull the pH and KH back up to a reasonable level (i.e., pH >7.4 and KH in the range of 80 to 120 ppm).

      Crash With Ammonia
      Special precautions need to be taken when ammonia is present due to its increasing toxicity with increasing pH. Unlike crashes where ammonia is not detected, recovery needs to be carefully executed to avoid killing your fish. The idea is to bring the pH up far enough to comfortably support life while at the same time minimizing ammonia toxicity. The following procedure also adds supplemental oxygen since ammonia affects the fish’s ability to breathe. Do the following procedure in order and exactly as written.

      Dose the pond with AmQuel at one and one-half times (150%) the manufacturers recommended label dosage. (If you've got spraybars run them at full-throttle and the outlook for your fish will be vastly improved.) Wait 5 minutes. Add drugstore-strength hydrogen peroxide (3% solution) at the rate of 0.25 to 0.5 cc/gallon. Wait a minute or two for the H2O2 to disperse throughout the pond. Add sodium bicarbonate (unscented household baking soda) at the rate of 1 cup per 1000 gallons. Add this dose to a 5 gallon bucket of pond water. Stir well until the water is clear (about 2 minutes) then distribute this mixture evenly around the pond. Wait five minutes, and then retest the pH. If the pH is still below 7.4, add additional sodium bicarbonate at the rate of 1 cup per 5000 gallons. Successive doses at this level may be made to achieve a 7.4 pH as long as sufficient time is allowed for the previous dose to become uniformly distributed (this prevents a pH test from misreading due to a locally high/low concentration of sodium bicarbonate).

      If you have the means to perform a partial water change, consider doing it. In instances where a high ammonia concentration is measured, this is a must. Fish which have been pH shocked and ammonia-tox'ed have a very poor outlook. Reducing the ammonia level by dilution after correcting the pH crash is an excellent strategy.

      Follow-Up For Non-Ammonia Types Of Crash
      Continue aeration for 24 hours. Once the pH has risen sufficiently and appears stable, re-measure the pH and KH in 12 hours and adjust either/both in the upward direction only as needed. Don't be surprised if your pH jumps to 8.0 or 8.2. Koi are perfectly happy at these levels. Feed very sparingly for the next week. Measure your pH, KH, and Ammonia levels daily for the next several weeks. Stop feeding immediately if any ammonia is detected. Monitor nitrite levels weekly for the next 2 months.

      Follow-Up For Crashes Where Ammonia Is Present
      Continue heavy aeration for 24-48 hours. Spraybars are ideal for this type of long-term support. Once the pH has risen into the low to mid-7, re-measure the pH and KH in 12 hours and resist further adjustments in any direction until the ammonia level drops to zero. If the pH swings over 7.4 to 7.6, redose the pond with AmQuel at half the label dose and begin a series of partial water changes (20%). Don't be surprised if you detect nitrites in the following two weeks. Biofilters can be severely damaged by the low pH levels encountered in a hard crash. Feed very sparingly (preferably don't feed at all) for the next week. Measure your pH, KH, and Ammonia levels daily for the next several weeks. Monitor nitrite levels weekly for the next 2 months. Carefully inspect your fish for signs of opportunistic disease.



      A Word About Sudden pH Changes
      Having just forced your pH to jump from sub-6 into the low-8's, you are likely to recall someone saying that *any* pH change greater than 0.2 pH points per day is bad for the fish. The truth is this: Any pH change is certainly stressful to some degree, but a sudden change toward the basic (i.e., numerically greater) end of the pH scale is tolerated fairly well by koi. It is sudden changes toward the acid end of the scale which typically kill fish in large numbers. I'll grant you that the huge upward change you just made is far from optimal, but recall that in a crashed pond, everything will be dead within just a few hours anyway. This adjustment was done as an emergency action and is a calculated risk. As long as you don't make a habit of these sudden adjustments, your fish should be fine.

      Prevention Of Future Crashes
      There is only *one* reason a pH crash ever occurs. Take a good look in the mirror and know your enemy. A pH crash is impossible in a pond where the proper carbonate hardness (KH) is maintained. Read that line again. It’s important. Ponds don't just "crash" unless they are seriously neglected. By maintaining your KH in the 80 to 120 ppm region, you'll never see another pH crash. Purchase a good pH / KH test kit and learn how to use it. Measure the pH and KH parameters weekly during the summer months and monthly in the winter months. Record your results. If needed, support the ponds carbonate level by periodic additions of small amounts of sodium bicarbonate or powdered limestone. Don't wait until your buffers are severely depleted to supplement your KH.


      Copyright © 1998 by Roark. All Rights Reserved.
      Email comments to: roark7@aol.com
      Page rev 7.12 of 06FEB98

      Batmasters aka Phil pointed out a great exchange:

      Batmasters 08-03-2007 09:16 AM

      Understanding pH and crashes-Help

      I just finished reading the sub-forum on water quality and found it really informative. Either I missed it, or it is not there, but what I'm trying to understand is why a pH crash occurs. The thread explains very well how it happens, and what to do, but not why. As I understand it, a crash occurs in a pond with low KH. According to the thread, it doesn't have to be ammonia or nitrite because they could be low as well. That being the case, what triggers a crash? The acid has to come from somewhere to cause the pH to drop doesn't it?

      I have low KH in my pond, but have never had a measurement of any ammonia or nitrite other than 0. Do I really have to worry about a crash as long as that remains true? Under what circumstances, other than ammonia and nitrite spiking, could the pH crash?

      Phil

      cppond 08-03-2007 09:39 AM

      Part of the nitrification cycle "consumes" kh. Therefore, the process reduces, and theoretically can deplete your kh. One school of thought is to keep the kh high in order to avoid that using BS, for instance. Another school of thought states that, presuming your source water has even moderate kh, regular water changes will replenish the kh and avoid a crash.



      Batmasters 08-03-2007 09:47 AM

      We have our wonderful Rocky Mountain water, almost no hardness. When I measured our tap water it was one drop for KH and 4 for GH. I'm aware of adding BS. If nitrification consumes KH, when KH was gone nitrite and ammonia would be over 0. Since I don't see that, then the KH is maintaining itself, just at a low level.


      Cowiche Ponder 08-03-2007 09:57 AM

      A large amount of rain can add the acid to the pond that can cause a crash. Seems that is what I read the most as a cause.


      cppond 08-03-2007 10:04 AM

      Your pond may never crash at a low ph if there is never an increased demand on the system. However, theoretically, something could occur to cause an increased demand, such as a spawn, etc.



      Batmasters 08-03-2007 11:47 AM
      *
      That's what I'm looking for, spawning and heavy rain are two possible causes. I'm guessing that increased fish load or fish growing might also cause problems in terms of stressing filters, but they would be slow or fairly predictable. Anything else?



      Brutuscz 08-03-2007 12:00 PM

      I had a ph crash 2 weeks ago in my indoor holding tank. My gh is 40-60 and kh 20-30 usually and tds=50. I noticed the fish had turned glowing red, and looked awful overnight. My ph test kit goes down to 6.2 and that's what it showed. Was probably way lower. All the fish died in that tank. In my own pond, I have 80lbs of calcite sand in the filter and add baking soda regularly. I just never considered it in my holding tank. Live and learn!!


      Batmasters 08-03-2007 12:18 PM

      I'm sorry for the loss of your fish. Any idea what changed, if anything? I'm really trying to get to the heart of this issue with this thread, not just for me, but for general information for all. My pond numbers are not much different than your indoor tank, a little higher but not much.My QT numbers are lower! I'm looking for long-term ways of changing hardness; the idea of adding BS weekly isn't appealing but I'll do it if I must to maintain the health of the fish.

      Phil



      Joey S 08-03-2007 12:21 PM

      Here's a good explanation of the chemical forces at work from Doc Johnson. http://www.koivet.com/html/articles/...article_id=206



      IMSALSMOM 08-03-2007 12:26 PM

      http://www.koivet.com/html/articles/...ater%20Quality

      I USE OYSTER SHELL. IT WORKS FOR ME, MY KH STAYS ABOUT 180.



      Graham 08-03-2007 01:41 PM

      Oyster shell is not capable of dissolving fast enough to prevent a PH crash. Heavy acidic rains can drp pH a like a rock and the shell would be playing catch up.

      KH is a constantly dropping number as every biological process in the pond is using it and then on a nightly basis the formation of carbonic acid drops it but gives it back during the day.

      So while 50ppm might be fine in a pond with very little algae or plants : one with green water could crash it out

      G


      Roddy Conrad 08-03-2007 10:10 PM

      When we feed our koi, the wastes create ammonia which has to be bioconverted since the ammonia is toxic to the koi. The biofiltration process of ammonia conversion consumes alkalinity by producing acid. So unless there is a constant addition to the pond of some form of alkalinity, the acid produced from feeding the koi will eventually consume the available alkalinity to give pH crash and loss of the biofiltration function. This will kill the fish if not corrected soon enough. No backyard fish pond can ever become “permanently balanced” without refreshing the alkalinity by water exchange, or baking soda addition, or other forms of alkalinity addition. Each pound of koi pellets added to the pond water causes the biofiltration to consume a half pound of baking soda equivalence in pond water alkalinity. In my own ponds, for each 25 pound bag of koi food used, I dump in a 12 pound bag of baking soda to maintain the alkalinity for the biofiltration to keep the water parameters optimized. For those lucky enough to have water supplies that contain reasonable levels of alkalinity, water exchange can provide the needed alkalinity refreshment. But if your water supply has low or no alkalinity, like my supply water, adding baking soda for alkalinity and pH control is the most practical approach. When the water source is above 100 ppm in alkalinity, water change is the usual preferred practice of alkalinity maintenance, but when the water source is below 80 ppm alkalinity, the addition of baking soda is usually required to avoid pH crash and to avoid pH variation.

      A pound of baking soda added per 1000 USA gallons increases the alkalinity by 71 ppm. Baking soda is pure sodium bicarbonate, available at your local grocery store for typically 40 cents per pound. I buy 12 pound bags of baking soda at the local Sam’s, since that is a more convenient quantity for our pond use. For most koi ponds, 80 ppm alkalinity is the minimum safe level to avoid pH crash for a reasonable time before checking the value with the next measurement. In koi ponds with higher stocking densities and feed rates (meaning mine, for example), higher alkalinity values are desirable for a safer alkalinity cushion to avoid pH crash and loss of biofiltration. The conversion of ammonia stops in the pH range of 6 to 6.5, since there is no longer any alkalinity to consume the acid produced by ammonia conversion. In my own koi ponds at their heavy stocking level, I prefer to maintain the alkalinity in the 150 to 500 ppm range with baking soda addition since the alkalinity drops 15 to 25 ppm per day at high koi stocking levels and high feed rates during summer months. If I tried to run alkalinity values below 100 ppm, or pH values below 7.8, I would have to add baking soda daily in my own ponds to avoid large pH variation and water quality problems that cause fish health issues. At the higher alkalinity values, the addition of baking soda is only needed once every two weeks.

      The ammonia in the pond water is much more toxic to the koi at higher pH values since more of the ammonia is in the unionized toxic form at higher pH values. So when the alkalinity is going to be increased by either water exchange or baking soda addition, the ammonia level needs to be checked until you are sure the filter is adequately converting the ammonia routinely. If the ammonia has built up to significant levels, meaning 2 ppm or higher, the safest practice is to chemically bind the ammonia with Amquel or ChlorAmX before making alkalinity and pH adjustment by either baking soda addition or water exchange.

      The biofiltration process performs better when the pH is in the 7.8 to 8.5 range, and the alkalinity is in the 100 to 500 ppm range. For instance, the basic research at Louisiana State University on the use of bead filters for intensive fish culture reported a minimum alkalinity requirement of 150 ppm for adequate performance of bead filters for conversion of ammonia and nitrite at high fish loads. All filtration systems are more efficient to bioconvert ammonia and nitrite at higher alkalinity and pH values, but many well aerated biofilter designs work well enough at alkalinities below the minimum 150 ppm value required for adequate bead filter bioconversion efficiency.

      There are two major requirements for the pH value of the water in a koi pond. The first requirement is that the pH be above a value of 7 to provide alkalinity for bioconversion as discussed above, since bioconversion consumes alkalinity and causes pH crash. The second requirement is pH value stability, since rapid variation in pH can stress the koi and cause both health problems and coloration loss. Higher alkalinity gives more stability to the pH value, and is healthier for the koi. The upper limit of good pH values for koi keeping is a value of 9, and the preferable range is 7.8 to 8.4, where biofiltration is at its maximum efficiency.

      Algae and other plant life in koi ponds can destabilize the pH of the water by producing carbon dioxide at night to give low pH at sunrise, and consume carbon dioxide in the day to give relatively high pH at the sunset. Higher alkalinity stabilizes this pH cycle.



      Batmasters 08-03-2007 10:27 PM

      Roddy,

      That is a great explanation and makes perfect sense. What I didn't realize is that the conversion of ammonia takes KH and thus the KH needs to be replenished simply because the fish are present. My water is very soft--so water changes won't make up the difference. I guess I buy stock in Arm & Hammer and go to adding it regularly. I like the idea of keeping it high so it is only necessary to add it every couple of weeks.

      My quest for trigger mechanisms is answered by this. There isn't one, simply the day to day operation of the pond, fish, and food can trigger a pH crash plus the rain and spawning as unusual triggers.

      Thanks
      Phil



      That was great info for me to consume, Bill. Thanks!!
      I started up my pond about 1 1/2 weeks ago and I am testing a high pH. I have a wide range liquid test from 5 up to 9 pH. My KH is 75 to 150 & Alkaline is in the 120 to 180 range. But the pH is still at least 9 according to a "Pond Care" pH test kit. It always comes out blue. I used the same kit on my Koi dealers water and that came out perfect looking, so I think I am doing the tests correctly. I have used "pH Down" for 3 days and still don't see an improvement. I tested my tap water, my source, and it is high pH also. My pond is mortared so that's giving off Alkaline right there, but unless I'm mistaken the Alkaline level seems alright. Will the pH come down to tolerable levels once the bio-reactor comes online or should I add some muriatic acid in safe amounts? I have 3 babies in there. If Muriatic Acid is a solution what amounts should I use?

      I am really worried I may harm my babies in that water.

      Thanks Bill,

      Mike

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