Had a quick hunt around and came across this comment on Clowns:
"They ... do not like to be alone. For example you have a community tank where there are fish of all different types but you only have one Clown Loach in the whole tank. It will then become lonely which causes stress, which causes their health to drop. So always make sure the Clown Loach has at least one or two friends around."
You might also want to think about adding a hollow log or tube as apparently they like to hang around inside with their noses sticking out watching everything go past.
I am getting Clown (and possibly Zebra) loaches in my next tank so any updates on him would be very helpful.
Cheers, Eddie