Clown Loaches should be kept in minimum groups of 5 and once fully grown at 8"-12" they require a tank atleast of 75 gallon.
please take heed of this advice.. at least 75g
you could get away with a 50g while the loaches are young, but they grow and mature fast and will definitely need a larger tank within probably two-three months.
check out this page, excellent and reliable information:
http/www.loaches.com/species-index/clown...ia-macracanthus
Good link, Yes, infact I would recommend a larger system once they're are fully grown, my 5 specimins shall be going into a 125 gallon tank. Then I will also make a bigger group, introducing more of them.
Mike
EDIT: They do not grow fast, infact they are known to be slow growing fish, so you normally have plenty of time to re-home them. They wouldn't need a tank in 2-3 months, perhaps 2-3 years. Infact, clowns can live in excess of 50 years, they can, if cared for outlive the owner.