Red bump under scales
My 4 inch comet goldfish has a red bump under his scales that is causing his scales to stick out a bit.
He seems fine otherwise - lively, eating fine. When I looked at it last night it looked like an injury pink with a red scratch through it but this morning it looks more red.
None of the others seem to be bothering him.
He is in a 90 gallon - ammonia 0, nitrites 0 - nitrates 20.
I added melafix last night (as supposed to be good with open sores/wounds) but all the goldfish went to the bottom of the tank and weren't looking very happy within 5 mins of adding it - so I did a 40% water change to remove some of it and they seemed to brighten up again.
Can't get pics he won't cooperate!