Put him to sleep about a week and a half ago. It took me a while to work up to doing it. By that stage he was extremely weak anyway- he was permanently upside down,and barely swam, although he was still eating a very small amount. Used clove oil, then freezer(couldnt drive a nail through brain, im too soft for that!)

He went very quickly,but I'm under the impression that he would've died naturally very soon anyway. Buried him in my garden next to my cat, as I didnt want to flush him. Its funny how attached you can get to a fish!!! lol

Got two new calico veiltails for my tank yesterday, to keep the surviving comet company, and they seem fine.

Thank you so much for all your help. Your advice was invaluable, because without it I know he could have suffered more without it. You are the only person who consistently gave me reliable advice and links. Thanks again!!