As I said complete novice.

The tank is not that big and when we bought it it stated it was adequate for 5 goldfish. However we only have 3 in it now but used to have 4 and they got on quite well. As for tank capacity and pump output I wouldn't have a clue as it was one of these buy in a box aquarium.

Water change I'm sorry to say this but it used to be just as it had a yellow tinge to it and then it would be all fish out into our standby tank which was filled the night before and then completely cleaned with treated tap water. As I mentioned in my previous message the water out our taps is as pure or purer than the stuff thats supposed to have been filter through rocks for 1000's of years. It is free from all elements and is ph Neutral. However saying that after reading numerous threads on here it is now changed 50-50 every week with the pump filter being cleaned externally through running water.

The fish are also fed twice a day with basic fish food which floats on the surface for a few minutes until it meets the pump then it gradually sinks.

With regards to the fish in question the blister has gone and so has part of its tail. I am assuming fish tails are a bit like hair and that it regrows after being sort of cut off. I have also been keeping an eye on the other fish and they all seem to be OK. No marks, spots or loss of scales.

So if you still need a picutre of what it was then I can send one to you and also if you can correct any of the things I am doing wrong then that would be handy too as my son likes his fish but since our chinese takeaway has got a fish tank and stuck Nimo and Dorey in the tank he wants some of those as well and can't seem to understand that they don't mix or at least I don't think they do.