My fish has a huge lump on it's left side, right behind the Gil and fin. I've separates him/her from my other fish to a new tank. He's still swimming about but the lump is almost half as be as he is.
It only turned up yesterday. Also his fin on that side has shriveled up and not moving.
What should I do?

Unfortunately, there isn't very much you can do. Most of the time when a fish gets an illness, you just have to prepare yourself for the fact that the fish is likely to die.

It sounds like Flukes from your description and it is treatable now and then but there is no guarantee.

Goldfish Disease and Goldfish Disease Diagnosis (http://www.desktopgoldfish.com/goldfish-diseases.php?disease=Flukes)

Sorry to be the one to tell you this but I have been through it all before.

Good luck to you.

Unfortunately, there isn't very much you can do. Most of the time when a fish gets an illness, you just have to prepare yourself for the fact that the fish is likely to die.

It sounds like Flukes from your description and it is treatable now and then but there is no guarantee.

Goldfish Disease and Goldfish Disease Diagnosis (http://www.desktopgoldfish.com/goldfish-diseases.php?disease=Flukes)

Sorry to be the one to tell you this but I have been through it all before.

Good luck to you.

Thanks for the help, I looked at some pictures of flukes but the lump on my fish is more like a swelling than that of those in the pics, there's no discolouration or anything. Is there anything else it could be?
Thanks