This posts were posted by JR a very experienced koi keeper, there is a lot of science in it and I just wanted to see your opinions.
First off, do not confuse TTs ( trickle towers) with Wet dry biofilters ( this would include the bakki shower).
TTs are NON- trapping filters. In fact they are useless as mechanical or prefilters. The idea of a TT is to have:
1) a huge non clogging, non-packing media , suspended in air so that falling water can ‘trickle’ over the surface in continuous thin layers. This allows for maximum oxygen contact with the bacteria/ammonia/nitrite reaction. It also allows for degassing of trapped gases within the water column ( various nitrogen gaseous forms).
2) If you think about it, a pond has a rather small surface area for its total water volume. Especially those ponds that are 8-12 feet deep. By using a TT, you increase your ‘water surface’ exponentially by running water over the media in thin layers. The water in the towers at any one moment can be viewed as an alternative water surface. Think of this gas exchange as a two way street- good gas in – bad gas out. Pumping air up the column while you run/trickle water down the column is an additional incentive for both bacteria and gas exchange.
Your column should be as tall as space will allow. 8-10 feet is good. I favor an air stone over a fan for air exchange as I want my entire media surface and walls of the TT to be exposed to high humidity. The ‘speed’ of the falling water can be slow or fast. But I have found water ‘trickling’ to be better than water roaring down over the media.
A wet/dry biofilter is very similar except most designs are also detritus trapping and therefore perform two roles- prefilter/mechanical as well as biological. These two functions are usually accomplished independently until one is at the expense of the other. In these filters, water can be run rapidly through the layers and probably should, as the trapped organics will have a tendency to ‘go off’ and produce excess decay/anaerobic conditions and gases in a slow gentle water flow.
The bakki show is the only wet/dry filter system in the world that claims the waste build up is harmless and even desirable. I remain skeptical about this claim and wait for the science to catch up to the marketing.
JR
‘Thinking outside the filter box’
This whole subject of biofiltration can be reduced to two issues:
1) the idea of two stages- mechanical and biological. And each designed to address organic and inorganic pollution separately.
2) the concept of biofilter efficiency Vs reduced biofilter activity ( the taming of an over active biofilter). This is a tricky balance to understand at first but is really very simple. Very efficient biofiltration is good and desirable, but excess biofiltration leads to excess nitrates. The ideal compromise would be a system that vents and gases off nitrogen and/or dilutes ammonia produced via continuous water changes and THEN efficiently removes the residual ammonia via normal nitrification. This results in very little fluctuation away from the ideal base line reading of common pollutants in general.
Here would be an example of a biofilm ‘evolution’ that changes/improves efficiency but is still ultimately quagmired in issue #1–
An under-gravel filter is made of three inches of coral rubble or volcanic rock rubble. It works very well and cycles very quickly- 18 to 22 days. It soon shows some nitrate readings. Over time the potential for anaerobic activity improves and channeling and reduced oxygen level prevail.
Now the undergravel filter is placed on a tray and moved above the water line- we spray water over it. It acts as it did before only it becomes more efficient. Much of the decaying waste vents it gaseous byproduct into the atmosphere and away from the fish. This is obviously a better outcome. Stage three- we create three trays of these ‘undergravel’ filters , all above the water line. Water falls from one tray to the other. This is now called a wet/dry biofilter. The gravel in the trays gets progressively cleaner as the first one or two trays acts as a mechanical strainer for organics as well as a biological reactor for inorganics. Most harmful byproducts of decay are gassed off. Organisms develop that feed on the organic slurry trapped in the filters. It is true that channeling occurs but the rich oxygen environment allows for maximum bacteria/oxidation efficiency within the sections of the media that are lowest in organic fouling.
JR
Clever boy!
So we still have the organic slurry 'in circulation'. This pollutant must remained contained, just like we would not want the slurry from a FF ( foam fractionator/protein skimmer) to leech back into solution once it is in the 'scum pot' of the FF.
A koi pond is destine to become a progressively nutrient rich situation. The gravel traps the results of this process, isolates it, vents the gaseous byproducts etc. But the passing water still recaptures a percentage.. This would include the cultivation and migration of those species that thrive on such organics. So we often see DOCs collected at the base of many wet/dry filters- large and small bubbles and suds that seem to immune from the normal physics that causes bubbles to poop! This is due to the ‘skin’ formed at the water’s surface as organic molecules cling to water and air. There are also things like POCs and TOCs in water subject to eutrophication. But that is another conversation.
Just suffice it to say, the result of all this, is water that has a higher than desirable, free bacteria count. The only way to counter this is with water changes, less fish and/or less food. In a system with stocking levels of one fish per 2000- 6000 gallons, you would likely get excellent results based on dilution factors. In systems of less than 250- 200 gallons per fish, I think you are going to hit ‘ the wall’ at some point. This is because the more the eutrophication of the environment, the less the carrying capacity of that water. This is the classic battle between heterotrophic species driven by organics and autotrophic species driven by primarily, inorganic ammonia.
And of course, the big test for all pond filter designs is in the season nature of ponds. As water cools and light periods shorten, the biology of a pond winds down. In this process, the slurry is no longer biologically neutralized. In Spring, you have pure pollution entering a ‘sleepy’ biological environment. In the old days this meant back breaking cleaning of stones and gravel and the painful work of cleaning lava rock. The alternative was to dump this slurry back into circulation. And that is why aeromonas was the scourge it was in the eighties and early nineties. Fueled by weak fish and unstable microbial activity, spring time and ‘dead winter water’ naturally encouraged the myth of aeromonas alley and the practice of over cleaning seasonal koi ponds.
Now having restated all this history, I have yet to see enough feed back on systems that are using Bakki exclusively, stocking normally and not heating in winter. These bits of info will help me mentally, to move the bakki shower out of the class of filters known as wet/dry biofilters.
And the single biggest reason for my skepticism regarding the ‘total bakki experience’ is that this would be the very first system in the entire world that combines mechanical/prefiltration and biological filtration in one stage and says that it is open-ended in that design approach, with no limitations over time/ seasons or stocking level considerations. In other words, it claims to be ‘immortal’ in performance and ‘immune’ to organic waste build up and seasonal disruption. A lot to swallow .
JR
Ian, I’m not sure if the proper response will put everyone to sleep that reads it! Bacteria can be lumped and grouped into many sub-categories based on :
Environmental preference-
*Temperature range/pH range/ORP ranges
*Oxidizing/ reductive nature
Behavioral preference-
* Use of oxygen, carbon dioxide in their metabolic activities
Physical characteristics-
* the general shape of individual cells.
* ability to produce spores or not.
* sedentary or gliding/swimming.
* how they absorb dye based within their cell wall construction
* the design and presence of the certain internal structures
For our purposes, we want to know if those species that use organic material for generating energy are producing toxic byproducts OR are potential pathogens by nature. The bacteria breaking down dense detritus and living in the base of biofilm is truly anaerobic and will only operate at very low ORP levels. And the byproduct can be nasty things like methane . Their activity can be more broad however and also straight forward- like the depletion of oxygen levels . Over time, this same environment also produces the second group - both opportunistic and dedicated pathogens.
People may not realize it but bacteria coats the entire pond, including the fish. The fish have a slime coat to protect them from bacteria damaging their living tissue ( and most common forms of heterotrophic forms are utilizing dead organic matter). But if a koi’s immune system is not working well or the slime coat is eroded away or the count of bacteria is astronomically large- these normally occurring bacteria will begin to infect living cells.
For our conversation, as water declines in quality ( LOSS of important micro and macro nutrients, buffers and oxygen molecules and INCREASE in organic content and inorganic nitrogen) the koi’s immune response is weaken by stress and at the same time, large numbers of bacteria like aeromonas, flexibacter and pseudomonas are produced. Once pretty much so much white background noise, these species now dominate the water column. In fact there is a tipping point where a simple water change can no longer dilute and bring things in line again. This is party due to the fact that these species are also gifted prolific breeders.
So this particular group of heterotrophic species are not so much about anaerobic toxic factories but rather about ‘utilizers’ of organic tissue. They still produce toxins but in the infection mode and this is what kills living cells.
So whether the species is one that uses organic material and produces gaseous byproduct or one that uses up organic fuel and puts a load on the pond’s carrying capacity, is not as important as why they are doing so well in a given environment. The secondary result of this environment will be the disease causing agents, once the dynamics of low ORP, low oxygen, high carbon dioxide and possible dangerous gases have done their damage to koi’s immunity and the normal balance of good and bad bacteria populations.
JR
This is my response to JR post
just a few queries I respect you as a very knowledgable person. You say that organic sludge builds up in a bakki shower system and overtime it is decayed by these anaerobic bacteria at the base of a biofilm.
Overtime this would lead to other pathogenic bacteria being more prominent in the pond. Would this not happen even more in a submerge system since the ORP levels are much lower.
And in most TT or bakki shower systems ORP levels are very high in the pond water would this mean that the pathogenic bacteria are less likely to occur compared to a normal submerged system
Last question ORP levels must be quite high in bakki shower systems at the biofilm/water interface. Is it ignorant to assume the majority of the biofilm is aerobic? and that with such high turnover top layers of the biofilm are removed and new layers are formed. As these new layers are exposed to water with high ORP there would be less chances of these anaerobic bacteria growing? And if they did they would probably be greatly outnumbered? thus in your scenario of these bacteria causing other pathogenic bacteria to proliferate would not be likely in a bakki shower/wet/dry filter pond. Since there are less anaerobic bacteria in a high ORP environment how is it that the organics decay and degas so effectively?
Thus in submerge systems there would more likely be a higher number of this anaerobic bacteria, would this mean that submerge filters can decay organics faster? That sounds good, but that would cause the scenario you described with low ORP and causing pathogenic bacteria to proliferate in submerge systems, especially with a settlement chamber that most likely would only be flushed once a day.
Lastly JR there are many systems that are bakki shower that stock more koi than 200 to 250 gallons and have not had the problems that you say will happen when the organic sludge build up. A few of these ponds have been running for more than 2 to 3 seasons. And a fair few of them still go through a winter period with pond water of 15 to 16 degrees. The problem you described may happen in 10 years time to a bakki showered pond but would that not be because the bioload has grown so significantly that really more showers should be added. Bacteria house in bakki shower is a great system but it will have its limits in regards to nitrification and degassing.
best regards
TEWA
ps I have always learnt a lot from reading your posts