my brother really likes to have a betta in his tank with his other fish, but i am not sure of one of the fish that is in there( i think it is causing the trouble). my brother is out of town for about a week, so yesterday i went to feed his fish for him. i noticed something was floating on top of the water, and i thought it was dead, so i went to take it out, but it was alive!! his poor betta has lost all of his back and top fin and only had one side fin as of yesterday. he is still alive, and scoots hisself over for food. today i went to feed his fish, and the betta lost his only last fin. the poor thing isnt eating, and barly swam away when i almost touched it.it only defense is to just roll around, but the other fish keep on picking at him and you can see his scales are falling off. i feel like i should maybe euthanis (sp?) him, but my brother is very protective about his fish. i could tell him it had just died, but i still dont know how to go about making his death quicker...what should i do.