By buying a fish in that condition you are encouraging the seller to sell more in the same condition. The only abuse there is that the fish was allowed to get into that condition in the first place. Would you buy malnutritioned and sick dogs from a breeder? Probably not. A person like that does not deserve any type of business. Also rescuing a dog is nothing like rescuing a fish. You might get a fish in those horrible conditions to recover somewhat but it will never make a full recover unlike a dog or cat. Do things right or don't do them at all is my philosophy.