My clown loaches usually squeeze themselves into some crevice in a peice of bogwood or somthing in the tank and rest in it for ages, i've heard this is pretty normal. I dunno about clown loaches "sleeping" out in the open though as mine don't do that, although i vaguely remember reading some threads a long time back about people reporting similar experiences with their clown loaches and apparently its relatively normal.
You should get your clown loach some companions though, as they are very sociable fish and enjoy the company of their own kind, and make sure that your tank is large enough to house clown loaches in the long term though and that its habitat is good too etc.
