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    Thread: Lost 50% of my koi over last 7 weeks... flukes?

    1. #1
      kuvesh is offline Junior Member
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      Lost 50% of my koi over last 7 weeks... flukes?

      Hi, my first post on this forum and looking for urgent help/advice.

      I live in Sydney, Australia so we have just gone into summer.

      My new house of 12 months came with an established 20,000L pond with about 35-40 large koi 30-60cm plus some goldfish. My guess is most fish 15+ years old.

      The pond filter is a gravity filter of approx 2000L. Its a very simple design where water circulates through a number of Japanese mats. Given the age and size of the fish, its must have worked well historically. There was no aeration in the pond other than as water return from the filter into the pond. I think the pump is 20,000L per hour based on the model number.

      Thankfully no major issues or fish loss since I moved in until November. However, since then I lost 15 large koi to mid Dec. I would find the koi in the morning on their back, sometimes still breathing fighting for life, but unable to maintain bouyancy. Goldfish were resilient but a few seemed to pinecone over the same period.

      In general koi behaviour became very unusual - very lethargic, flashing, red streaks, stayed at bottom of deep end of pond, some had locked fins, very low appetite.

      I have closely monitored water quality / done frequent 25-40% water changes and put in more aeration but still no improvement.

      My self diagnosis was bacteria or parasite. I salted the pool to 0.6% for 1 week. Fish became slightly more active. No deaths for a week and then I lost another couple.

      I chanced across a Fish Vet who made a house call. She scraped a few goldfish didn't find anything (we couldn't net any of the koi). She suspected parasite from the pale gills but thought the salt level may have been a factor for not finding anything. She told me to reduce the salt level and she would do a second visit.

      Over next 2 weeks reduced salt to 0.05%. The vet returned after I lost a other couple more koi. We did a scrape of some of the goldfish and she found flukes.

      She prescribed 200g of praziquantel powder for my 20,000L pond. She said with this type of fluke one treatment would be sufficient. She also said we should inject anti-biotics into the fish to address any secondary bacterial infection. Given the number of fish and difficulty in netting them, she gave me some powder antibiotic to coat the fish food instead. She also asked me to increase the salinity to up to 0.3%.

      Its been 48 hours and the fish behaviour remains strange post the praziquantel dosing.

      All the koi have now moved from the deep end of the pond to the shallow end, and appear to be floating close to the surface. I donít see them gasping for air but they are very lethargic and zero appetite. A positive is flashing is seldom which suggests to me the praziquantel may have been effective in addressing the flukes.

      Given the zero appetite, I have not been able to start the antibiotic treatment through the food. This coupled with the behaviour of the fish continues to make me very concerned.

      Appreciate any feedback from others on whether this behaviour is expected and their appetite will return or I should be taking other measures to save the fish.

      FYI, my current water quality readings are below based on API test kit. I donít have a KH test. Thanks in advance.

      Ph 6.5
      Ammonia 0-.25ppm
      Nitrite 0-0.25ppm
      Nitrate 0-5.0 ppm
      Salinity 0.3% (digital meter)

    2. #2
      pugsandkois is offline Junior Member
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      i think you have to do a 50% water change 3 days after using aqua-prazi and do another treatment to kill the new flukes that hatched. then maybe a third time to be safe. once that is done. i would treat the pond with potassium permanganate. this will reset your filtration system but it would knock out any other parasites you may not have accounted for including, chilodonella, apiosoma, trichodina, and costia. A mixture of malachite green and formalin will help with parasites and bacterial infections as well. melafix is also good for bacterial infections and fungus, it helps the koi regrow damaged fins and tissue. good luck

    3. #3
      pugsandkois is offline Junior Member
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      the pine cone in your goldfish is dropsy, if multiple fish have displayed this disease it is most likely a cause of viral infection. dropsy is due to retention of fluid within the tissue and abdomen. it might be that your filter is not being cleaned of detritus enough and the bad bacteria is accumulating in this area and infecting your pond. you need to do more frequent water changes and clean your filters more regularly. this will help in reducing the pathogens in your pond. i would also add some air stones to help with the osmoregulation of the koi. since they are bigger now the pond may not have sufficient oxygen to sustain that many fish.

    4. #4
      pugsandkois is offline Junior Member
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      if you do try some of these other meds, make sure the salt wont interact negatively with the treatment you choose. if it does then you would have to reduce the salt level significantly through water changes first. good luck.

    5. #5
      SimonW is offline Senior Member
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      Usually fluke will not so quickly kill koi. I think that fluke is probably a secondary problem.

      I wonder if you have done anything unusual to the pond within the 2 weeks prior to the koi showing problem?

      If you have not done anything special then I would think that pH-crash could be the cause. pH 6.5 is quite low, so I wonder if you have been doing anything to keep the pH-level stable?

      Frequent addition of NaHCO3 is the best way to keep stable pH while feeding the nitrification bacteria with carbon.
      Last edited by SimonW; 01-06-2021 at 01:32 PM.

    6. #6
      mplskoi is offline Supporting Member
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    7. #7
      coolwon is online now Senior Member
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      Could they be suffocating through the lack of oxygen as well as the parasites attacking their gill.

      Try and work out how many fish your size pond should comfortable handle.

      If you have lost so many fish, it could have been overstocked.

      I believe in turning that stale, mature water down in the lower layers over and over to constantly interface and get the % oxygen content up in all the water equal.

      No dead spots

      How much rain have you had? Low. Ph reading.



      Garfield
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    8. #8
      kimini is offline Senior Member
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      Quote Originally Posted by SimonW View Post
      ...I wonder if you have done anything unusual to the pond within the 2 weeks prior to the koi showing problem?...
      This is what I was going to say. Given that this was a well-established pond with apparently no previous issues, it does seem to point toward something changing recently. Added fish, chemicals in or even around the pond (like, house paint fumes, termite tenting fumes, things typically done to a home being sold), incoming water quality changes? Though maybe coincidental, I suppose it is possible that the filter loaded up about the time you bought the place, and it's been getting nasty. I don't know enough about diseases to be of any real help, and will sit down now...

    9. #9
      RichToyBox's Avatar
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      It is hard to tell what may have transpired, but to look toward the future, I would start with a KH test kit. KH is responsible for stable pH which is needed for both the fish and the filter. You can probably tell as much by running the pH at near sun up, and again at sun down. Due to photosynthesis, if the KH is not high enough, the evening pH will be high and the morning pH very low.A KH value of over 80 will tend to provide somewhat stable pH values, and if the KH is between 100 and 300 ppm then the pH should be rock solid. The most prevalent contributor to KH is bicarbonate, which is generally available in waters from sources where it has traveled through limestone, and the artificial addition if needed is through the addition of baking soda, bicarbonate of soda, sodium bicarbonate, ... depending on local descriptor. With the bicarb as the ion providing the KH, the pH will be near 8.3 usually.

      Getting sick fish to eat is difficult and as a result it is very difficult to get the sick fish to take the antibiotic food. You would do well to get a set of koi nets, a flat pan net and a sock net, and learn to catch the fish so that you can give injections. There are YouTube videos on catching koi and after getting familiar with the use of the nets, it becomes fairly simple. Without a good flat pan net of about 700 to 750mm diameter, it can be very stressful on both you and the fish.

      As has been mentioned, flukes are only one of many parasites, and the others are readily killed with a formalin/malachite green solution, but should also be susceptible to salt, so with the 0.6% salt, you should have taken care of them.

      I would start with getting the pH stable and then worry about the other issues.

      "Our goal is to assist with emergency and Koi health issues, as well as educate on best practices. Please help us gain a clear picture by giving the original poster time to answer our questions before offering opinions and suggested treatments."

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    10. #10
      KTownKoinut is offline Senior Member
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      Shouldn't a 20,000 L pond only have about 20 large koi???

    11. #11
      coolwon is online now Senior Member
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      Maybe the air pump got handled during the sale of the house?

      Sydney daily temps get quite high in summer. Lower oxygen levels in over crowded pond.

      Garfield
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    12. #12
      kuvesh is offline Junior Member
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      Thanks for the feedback.

      Fyi, I got a API KH test kit today. Took 9 drops which I think indicates hardness >100 which I think is good.

      I also added 8kg of sodium bicarb. The PH only increased from 6.45 to 6.6 which was frustrating because i might need to add 30+ kg to get to 7 ph at this rate.

      Also the bicarb approach concerns me because its not sustainable to continue adding this volume of bicarb on each water change. My tap water is 6.5ph....

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    13. #13
      coolwon is online now Senior Member
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      8 kg of sodium bicarb in 20,000 liters of pond water with fish.

      Could your Ph test kit be giving a false reading?

      How are the fish behaving?

      Garfield
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    14. #14
      kuvesh is offline Junior Member
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      Quote Originally Posted by coolwon View Post
      8 kg of sodium bicarb in 20,000 liters of pond water with fish.

      Could your Ph test kit be giving a false reading?

      How are the fish behaving?

      Garfield
      I checked again this morning. API test kit says 8...

      As i was adding the bicarb yesterday i only monitored with my digital reader which has obviously given a false reading!!! That goes in the bin.

      Fish still lethargic with no appetite but are now congregating in groups rather than all in the same area.



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    15. #15
      icu2's Avatar
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      Calculator for baking soda:

      https://www.koiphen.com/forums/koicalcs.php?do=calckh

      Multiply 17.86 x number of drops for KH.
      --Steve

    16. #16
      coolwon is online now Senior Member
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      How did you come by the 8 kg number for 20,000 liters.

      Garfield
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    17. #17
      kuvesh is offline Junior Member
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      Trial and error. I was just trying to move up the ph by adding and testing with the digital meter (which has been proven inaccurate). I read online that you cant overdose sodium bicarb and it was better to raise the ph than keep as is.

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    18. #18
      coolwon is online now Senior Member
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      Would you have friend you could borrow an air pump from and see what sort reaction you get from turning the water over.

      60 or 80 liter pump and enough air stones to get rid of the air the pump delivers (No build up of back pressures to blow the diaphragms)

      An air pump will never go to waste if you intend keeping fish.

      Garfield.
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    19. #19
      kuvesh is offline Junior Member
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      Quote Originally Posted by coolwon View Post
      Would you have friend you could borrow an air pump from and see what sort reaction you get from turning the water over.

      60 or 80 liter pump and enough air stones to get rid of the air the pump delivers (No build up of back pressures to blow the diaphragms)

      An air pump will never go to waste if you intend keeping fish.

      Garfield.
      Yeah, air was the first thing i added in mid December. I got 6600L/hr pump and have 5 airstones around the pond.



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    20. #20
      coolwon is online now Senior Member
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      Are the fish near the bottom with clamped up pecks.

      Drag a net across the pond to one end and take some gill and scale mucous slides and see what you come up with.

      Choose the most miserable looking fish to pull the samples from.

      Garfield
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