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    Thread: Koi have died from unknown- How to clean out pond to make sure it is safe for new

    1. #1
      Zac is offline Junior Member
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      Koi have died from unknown- How to clean out pond to make sure it is safe for new

      Over the past two days our KOI have started to die.

      It was a total of 11 in the pond currently only one is left who is slowly breathing on his side along the rocks. We have tried everything, salt, primafix, Melafix, Microblift BSDT.

      It was so sudden most of them were about 10+years old from 12-18 inches. They died one at a time. We did find about a week ago a frog dead in the pond. We dont know if this was the "host" or the warning.

      My family is distraught and we cant really cry anymore. My question is what do I do to make sure what ever is in the pond dies off before adding new fish.

      We have done partial water changes in between deaths.

      What is the procedure to decontaminate a pond after a massive death?

    2. #2
      icu2's Avatar
      icu2 is online now Administrator ~ WWKC Treasurer
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      Welcome to Koiphen and I'm so sorry for your loss.

      Can you give us any tests for ammonia, nitrite, nitrate, KH, and pH?
      Obviously it won't help with the fish already lost, but it might help fixing things when they're replaced.
      Any new fish added when the deaths happened? Condition of the pond? Filtration? Rocks in the bottom?
      All helps getting down to what happened.
      --Steve


      In the beginning of a change the patriot is a scarce man, and brave,
      and hated and scorned. When his cause succeeds, the timid join him,
      for then it costs nothing to be a patriot.

      ---Mark Twain

    3. #3
      Zac is offline Junior Member
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      Thanks for the reply.

      The pond bottom is liner, I was going to add river rock, but well not now. No new fish were recently added, this was really sudden without NO warning, except for the frog. After the death of the first fish (the biggest at almost 20 inches) my water tests came back amazing with no issues. We have always had high PH and it never bothered the fish, never seen them flash at all. The pond had great water flow and bio filtration with MicrobeLift Professional Contractor Bacteria added weekly.

      Water Source: Private Well, filtered at end of hose.
      Gallons- 390 (+/- 50 Gal)
      Avg Depth- 2 foot
      Age of pond: 31+ years
      Features: Biofall Stream, Aerator, Liner pond, External Aquascape 3500 pressure filter and micro skim ultra skimmer box, 28Watt UV light has been off. Pondboss 5,000 GPH Waterfall Pump

      Test Results
      Nitrite: 0
      PH 8.2
      Ammonia: .5
      Phosphate: 0
      Hardness: 250
      Chlorine- 0
      Water temp 70
      Alkalinity- 80

    4. #4
      Rich8888ri is offline Senior Member
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      I will let the experts answer as this does seem mysterious if no koi were added. When was the last time a koi was added? (if last year at the end of the season when water temp was cool then maybe fish could of had khv and you wouldn't know it until temps warmed up this year.)
      Also are you using test stips or liquid? The strips are very unreliable and your amonia is high so could be much higher if you used a strip.
      Other than those 2 things i don't know where to go with it. You didn't mention KH reading but with ph that high it doesn't seem to be a ph crash.
      Last edited by Rich8888ri; 3 Weeks Ago at 01:34 PM.

    5. #5
      Zac is offline Junior Member
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      Liquid test kit. No fish have been added in years. Only visiting frogs. The nearest body of water besides our pond is far away.

    6. #6
      icu2's Avatar
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      11 - 12"-18" fish in 390 gallons is very overstocked. At this point it's almost impossible to tell what killed them.

      Diluted (10ml/liter) bleach is a good disinfectant or a product called Virkon Aquatic. I'd run the pond and filtration
      for 6-8 weeks after treating before adding any fish... and I'd only re stock with goldfish with 390 gallons.
      --Steve


      In the beginning of a change the patriot is a scarce man, and brave,
      and hated and scorned. When his cause succeeds, the timid join him,
      for then it costs nothing to be a patriot.

      ---Mark Twain

    7. #7
      RichToyBox's Avatar
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      As mentioned, it will be very hard to tell, but with that many fish that have been in that environment for that long to die so fast, I would think that it was probably some form of poison. Possible candidates are pesticides used in the lawn or garden, on trees nearby, herbicides for weed control, etc. If poisons, then I would treat with about 4ppm Potassium Permanganate, before or after treating with bleach to kill any possible parasites, bacteria or viruses. The filter will be hammered so introducing new fish after all treatments have been neutalized, should be slow, allowing the filter bacteria to reestablish. Monitor ammonia and nitrites during the cycling/reestablishment of the filters.

      "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."

      Zone 7 A/B
      Keep your words sweet. You never know when you may have to eat them.
      Richard

    8. #8
      Zac is offline Junior Member
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      Lets bring back some attention to the frog that was found about a week earlier. Could that happened to introduce a bacteria into the pond? Do I have to be concerned with the birds who splash around in the stream? My mom described it as being big bloated smelly and nasty. Today while decontaminating I found a frog in the pond who seemed to be just fine.

      Also what about the water quality test, if my test showed zero ammonia that would mean the biological filtration was working right?

    9. #9
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      How many gallons is the pond? Earlier, you said 390, but wondering if there were some zeros left out.
      TurtleMommy

    10. #10
      RichToyBox's Avatar
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      Frogs can carry parasites and birds have been accused of carrying parasites, but I really don't believe it was parasites as the deaths were too many too close together without signs or symptoms lasting for long enough to raise concerns. For there to be that many fish killed that fast, it would have to be some form of poison or the addition of something like Clorox. Mean little neighborhood kids, nasty neighbor, or accident by the yard maintenance group. Very possible that whatever it was also killed the frog.

      "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."

      Zone 7 A/B
      Keep your words sweet. You never know when you may have to eat them.
      Richard

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