in my experiences keeping blacks, unless your water is super clean, the fins will be tattered. Idk why but the blacks fins are super sensitive to water conditions. You might want to test the water before you buy but if its eating thats a good sign. Im sure if you take good care of the fish the fins will heal but will not be perfect. fyi blacks sell for $45/ 3" here in Hawaii. good luck, but i would get a lei LOL