Many thanks for reply, I took it out of the tank last night, It was ok yesterday morning when I was looking in the main tank, so guess it all happened during the day yesterday. It's not really rolling around just has difficulty being the right way up as has hardly any fin left. I'm pretty sure it won't make it to be honest, i have done a water change today and put in a little melafix.

I just hate to see the poor little thing suffering. I just wasn't sure if it would be best to put it out of it's misery but then I wouldn't know the best way of doing that either.