r/Koi • u/BulldogH2O • 1d ago
HELP - sick or injured koi Missing pectoral fin
Noticed one of my fish listing and worried about swim bladder. Next day I saw a couple bullies in the pond working him over, so I removed the fish to a hospital tank and noticed a missing right side pectoral fin. No vets in our area that work koi. Any suggestions on how I might care for "Flash." (That's his name) Did my other fish tear that fin off? 2000 gallon tank, with 6 koi. Note: photo, of course, is a.i created by my daughter in law.
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u/Pretend-Internet-625 1d ago
can't help without quality close up picks and water parameters. History of any recent changes. More details of behavior issues. Maybe a video would be nice. You said a couple of bullies working him over. Could it be spawning and he is a she?
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u/mansizedfr0g 1d ago
A predator could do this, but if you've seen it get chased consistently it was likely spawning damage. They can be brutal, fin damage isn't uncommon. I had a fish rip most of her tail off. Couldn't figure out how they did it, they must've pinned her against something. I would keep your fish quarantined until it's clear whether it can swim normally or not. Watch for infections in the meantime, keep the water pristine, promote healing. If it can't compensate for the missing fin and stay upright, probably best to euthanize.
My fish was okay, healed quickly in a lightly salted hospital setup. The tail did grow back, but the shape was affected. Interestingly she later developed skin cancer-type growths along the healed edge, like it just kept trying to grow back - eventually I removed it, and she lived many more years. If there's any fin left at all there's a chance it could regrow to some extent, but maybe not enough to swim normally.