He has a big tumor at the base of his tail. It has been growing at an accelerated rate the last 2 months and is getting very big. He doesn't swim as good as he used to.

Here are some pics: http://imgur.com/XQudng4, http://imgur.com/OEGf6Fa

He is about 5 years old.

I don't know how big I am supposed to let it get before putting him down. I figure I will need to eventually, and just want to be prepared for when that day comes.

Also, when that day comes, what is the best way to put down a fish? I have heard that clove oil is a good way, is that true? I have also heard that freezing is the wrong way. Any advice would be helpful.

Edit: Also, if anyone can tell me why one of his eyes is so much bigger than the other one, I have been wondering about that too. I don't know if he can see out of that one.

His name is "Chosen One", but maybe I should change his name to "Lucky" :(