Just got this guy from Petco today, and he's in a very dilute AQ salt treatment tank right now (1/4 tsp to 3 gallons). Partially for his fins, partially to ward off any diseases he might have developing from living in a cup for who knows how long. I'll be upping the dose to about 1tsp/1gallon slowly over each water change until those fins heal. Anyway. What I would like to know is if you all think its biting or rot? He's got a decent chunk missing of his caudal fin, and what looks like a tear in his anal fin. I'd flare him for better pictures, but he doesn't like the camera, and I don't want to stress him with that until he's settled. But he does flare at the mirror, so if its an absolute must to see the extent of the damage, I can try.
I didn't think it necessary in this case to fill out the questionnaire, but I will if asked.