a troubled fish

Question
my fish is leaning to its side and whenever it floats to the top of the tank its seems to drop back down as well. its seems quite depressed and i have observed black discoloration  on its fin. its a normal goldfish

Answer
The black discoloration could be Black Spot Disease. I would suggest going to the pet store and picking up some ammonia testing strips to check the ammonia levels in your tank. Sometimes black marks on goldfish can be caused by ammonia burns. If your levels appear higher than normal you will have to purchase something to lower the levels in your tank. If your fish continues to get worse you may have to get a broad spectrum anti-biotic.