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Thread: Are they eating each other?

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    brianm1962 is offline
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    Are they eating each other?

    I have my koi inside for the winter - mink problems.
    I was away for 5 days and returned to 3 dead fish. Upon further investigation, I discovered that a number of the fish look like they have been eaten from the outside-in. I had my water tested and everything was fine. I took a fish to the store, and the only explanation they have is that they are eating each other.

    I have one large fish - 14" or so, and a number of smaller ones (3"-8"). The large fish is fine. I have created a temporary divider to keep the large guy away.

    I feed them daily for about 3-4 days, then I am often gone for 5-6 days.
    Water is changed every 2-3 weeks.

    Do you think the big guy was eating the others?
    Is there anything more I can do?
    Will the ones that still have chunks taken from them recover?

    Thank you for any advice.
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    I don't think so. Usually the first thing you see fish on fish aggression is frayed fins. That fishes fins are untouched. Some nasty bacterial infection would be my best guess but I never seen anything that bad before.

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    Well come to think of it, do you have a pleco or algae eater in with them?

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    this should be moved to the ER
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    I'm going to move this to ER so experienced folks there might be able to help and they keep their finger on the pulse of that forum. Hope you get some answers, that is nasty looking and I am surprised the fish is still alive. I feel sure they will suggest you heavily salting the water and warming it up.
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    Quote Originally Posted by Wolfhound View Post
    I don't think so. Usually the first thing you see fish on fish aggression is frayed fins. That fishes fins are untouched. Some nasty bacterial infection would be my best guess but I never seen anything that bad before.
    I have a large bio-filter with active carbon. That's it.
    The environment has been stable for 2 months. Not sure how any new bacteria could have been introduced. But as a precaution, I'm willing to add any chemical that might help. I am open to suggestions. I have salt already.

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    Koi don't eat each other. If no other fish, then maybe caught in the bottom drain or some other sharp object. Keep all the fish together. Time to start with salt if any hope of saving this one. Dose with 1 pound/1000 gallons or 1/2 pound for 500 gallons. That's the ratio to start with. Then add the same amount in 8 hrs and the same amount again in another 8 hrs.

    Warm water will help, but I don't see much hope for the one in the pic. How bad are the others?
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    Quote Originally Posted by Joey S View Post
    Koi don't eat each other. If no other fish, then maybe caught in the bottom drain or some other sharp object. Keep all the fish together. Time to start with salt if any hope of saving this one. Dose with 1 pound/1000 gallons or 1/2 pound for 500 gallons. That's the ratio to start with. Then add the same amount in 8 hrs and the same amount again in another 8 hrs.

    Warm water will help, but I don't see much hope for the one in the pic. How bad are the others?

    Actually Koi can, and do, get cannibalistic on sick or dying Koi. I have experienced it. It was usually larger ones eating the smaller ones. This one pictured could have been picked over if it was sick but usually they eat the eyes as well so I am not sure it is what happened.
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    Quote Originally Posted by Russell Peters View Post
    Actually Koi can, and do, get cannibalistic on sick or dying Koi. I have experienced it. It was usually larger ones eating the smaller ones. This one pictured could have been picked over if it was sick but usually they eat the eyes as well so I am not sure it is what happened.
    Well, you have seen things that I haven't, I guess. When I've had an ailing koi, the others in the tank usually try to help their sick buddy. The Koi pictured looks like something tried to "filet" it with a knife. That's why I was thinking it got sliced on something sharp in the tank/pond.
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    Quote Originally Posted by Joey S View Post
    Well, you have seen things that I haven't, I guess. When I've had an ailing koi, the others in the tank usually try to help their sick buddy. The Koi pictured looks like something tried to "filet" it with a knife. That's why I was thinking it got sliced on something sharp in the tank/pond.
    Definitely, nothing cut it. It is either parasites, bacteria, chemicals or another fish.
    Even the bio-filter and pump is in another tank. They cascade into one-another. The only thing in the tank with the fish is some 6" clay pipes (so they can hide) and a bubbler stone.

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    Unless you added chemicals, I would eliminate that. Would also eliminate parasites or bacteria. Neither "attack" in one large spot. I don't suspect another fish unless you have something other than much larger koi or ?? The clay pipes could be a possible. Although smooth on the exterior and interior, the edges can be almost razor sharp. If spooked for some reason and jetted into the clay pipe, it's possible to take a chunck out.
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    Bacteria is more than likely the culprit in my opinion.
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    Quote Originally Posted by Russell Peters View Post
    Bacteria is more than likely the culprit in my opinion.
    Any recommendation for treatment?
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    How about some really clean water to start?

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    Quote Originally Posted by Joey S View Post
    Any recommendation for treatment?
    I have seen this in Tosai in Japan and don't know what they do. It is really odd but it looks like the bacteria just eats the top layers exposing the flesh. On the fish posted here it looks like there is a slight infection around the perimeter of the wounds. I would try clean water, salt to 0.6% and El Bagin. Warmer water would aslo help but it would be important to not heat up the water too fast.
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    Wow I'd Euthanize this one if it were mine.
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    I would seperate the affected ones and treat them with antibiotics. Furan 2 has worked well for me. I usually treat the fish in a bucket with an aerator and every day I move the fish to another bucket with clean water and retreat with antibiotics. This keeps cost down instead of treating the whole system. I don't think you will be able to save any as severe as the one in the pic.

    On your main holding tank & unaffected fish I would treat with melafix/pimafix combo as a precaution. This has worked well for me on mild bacterial infections or as a preventative. It doesn't work too well on serious bacterial infections.

    Most of the bacteria that cause infections are always present and only cause a problem when the fish are stressed. Water quality (ammonia, nitrite, or high DOC's) is the usual suspect.

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    I have seen this where the fish gets an infection or a parasite and keeps flashing until they wear the skin off. I have had good luck putting the fish in a quarintine tank and treating every other day with debride ointment and a powdered antibiotic, I can't remember the name of it. It took the fish about a month to regrow the skin it had scraped off.

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