Fish Injuries...Any Ideas?
So a couple weeks ago, I noticed a Rasbora that had some fungus type of stuff around the area where the tail fin meets the body. Looking closely, it seemed to me like it was injured and the maybe the fungus set in. It never spread to any other fish. Then, about a week later, my wife found a Von Rio Tetra struggling with most of it's rear fin gone. This was not a progressive thing from disease. One day all is well, the next he was tore up.
Both followed 50% water changes but that might be coincidence. My fish list is fairly common and is made up of different small, peaceful types of tetras, rasboras, danios, cories, bristlenose's, hatchetfish, a whiptail, a dalmation molly for my daughter and 2 gudgeons. Sometimes the fish will chase each other a bit but I've never seen any real aggression since I got rid of my betta and dwarf gourami's a while ago.
I do have some nerite snails, amano's, ghost shrimp (not lookalike prawns) and one bamboo shrimp. For equipment, the only thing that could do this type of damage is my Koralia Nano 240. I would like to say that both injuries happened at night but I'm not 100% sure.
The only things I can think of would be run-ins with the Koralia or maybe the bamboo shrimp. I've heard the shrimp can do this if they are too hungry but mine seems plump and quite red. He filters until I shut down the filters to feed my fish, then he forages and goes back to filtering later. To be safe, I went back to feeding him before I feed the fish.
Any thoughts about what might be going on?