I am in no way a gold fish expert, I have one, it is actually my kids' but I get to take care of it. Around Wednesday I noticed the fish looked like he had black fringe on his tail, I thought maybe he had always had it but I just didn't notice before until a couple days later the black had spread. I don't know if this is normal or if he has some kind of fungus or something and if it is a fungus how to treat it. He is the only fish we have, I change his water and clean his tank weekly and he is about a year old. He is in a two gallon tank, the same tank he has been in since we got him and I just feed him regular gold fish food and we use Aquasafe to condition his water.

He's most likely suffer ammonia burns due to a high level of ammonia in the water.Injured areas turn black when they are trying to heal.Goldfish require 10 gallons each at the very minimum.I prefer 20 to 30 gallons per goldfish personallybut 10 will suffice.A 2 gallon tank cannot cycle and this is why the ammonia builds up from fish waste and other things.It takes 3 to 5 days for ammonia to get to decently high levels so by a weeks time the fish is getting burned from it

He needs 10 gallons??? Well at least I haven't kept him in that tiny fish bowl they sent him home in! I will buy him a new home tomorrow and see if that helps him.

Just a word of caution: even in a 10 gallon tank (and that is most definitely what he needs), you will still have to cycle the tank, that is build up enough good bacteria in the filter - and you will have to install a filter - to extract the toxic ammonia and nitrites from the water. Have a look at 'cycle of the tank' on the left hand column for more info on this, or post again if you're not sure what to do - we can guide you through it.

Oops!I sometime forget some people dont know about cycling or how to cycle.Sorry about that.Thanks for catching that emma.