When we moved into our house about four years ago we removed the goldfish from the pond as we have cats and we felt he'd be safer inside in a fishtank.
When we bought the fishtank we also bought him a little goldfish friend. One of the fish has had a bump on its head for about three years now. We don't know if it's pond fish or pet shop fish though.
We asked for advice at our local aquatic centre and they tested our tank water for nitrates ect. They said everything was ok but gave us drops to use, which we do. I asked if he thought the fish was in pain and he said if he's swimming about and eating then probably not and that these bumps aren't uncommon.
The bump split about a month ago and had a yellow lump in it which came out and we removed it from the tank. The bump still has the hole but all the open skin has healed. We hoped the bump would go but if anything it's now much larger and pushing his eyeball down and into his head. It certainly looks uncomfortable.
I think now is probably the right time to put him out of his (possible) suffering. Will a vet do this and would it be done by an injection or something in the water to put him to sleep? I couldn't bear for him to be taken out of the tank and suffocated.