I can home from work this afternoon and found my zebra danio swimming in a circle. When I watched him I realized he was missing most of his fin on one side and had two chunks missing. I euthanized him but took a couple pictures because I don't know if this is from a fish fight or a disease.



I looked at everyone else in the tank. They all look fine and with the exception of an oto they are all accounted for. This tank only has platies, corys, otos and the longfin zebra danios, none of which I have ever seen get aggressive.

If this is a disease what do I need to do to treat it? I suppose a water change is also in order, although I just did one last night.

Thanks in advance for any help

I don't know small tropicals that well, but my first guess would be the platies picking on it. Maybe not trying to eat it just harassing it. My guess from my limited knowledge.

Clint