Really don't know how this happened! Only thing I can think off is he ate the aquarium salt my girlfriend put in there to treat her parrot fish. I've had no aggression and no problems in the tank. I introduced a 2" Flowerhorn last night too , but I really dont think the Flowerhorn did it. Him and the EB were getting along fine last night. I'm really upset about this, by far my favorite fish I own.(ed). Only fish in the tank with him was 1 2" Flowerhorn, 2 3" Sevrum, a 5" BP, and a Syndontis cat. All have been living together for over a month and no aggression! I'm thinking the salt did him in :'(. Any other ideas? He wasn't really beat up so idk! Just really tore up about it...