Thanks everyone,
I've moved him to another tank to try to give him a break from stress of krusty the clown loach annoying him, he's the biggest of the con's in the tank and theres only the clown who harrasses him, I think the clown has a personality disorder and the con is just neurotic!
The tank i've removed him from has been running very well for some time now, no water problems and very clean, he's now got 45g of tank to himself, i'll see how he goes and may just leave him there.
I'll do another change on the main tank today, but as I said the other fish look fine.
Thanks again everyone, I hate it when the little'uns get sick.
PS. It was my 4 year old son called it krusty the clown, the isolated con has now been named Spot ( because he's stripey! )