Clowns do best in groups of three or more. Recommended tank size is 75g. They grow really fast the first year then slow down but need lots of swimming room. Here's some excellent information
http://www.loaches.com/species-index...a-macracanthus
I too feel the one you have needs to be returned or re-homed unless you can provide it other Clowns to school/sleep with and a much larger tank.
Clown Loaches we see in the pet stores are most likely wild caught.
Hope that helped.
carol
Clowns aren't sexually mature until they are about seven years ago and females are much chunkier than males. They have been bred by professional breeders using hormones other wise to my knowledge they haven't been bred in home aquaria.