Thanks for all the replies! I guess I'll give up on trying to use snails to aerate the sand. Is there anything else that would burrow and do that that the loaches wouldn't eat?
Mine (Zebras) are in a fine gravel bottom tank but are allways digging in the substrate in the hope of finding a non-existant snail. Depending on how deep the substrate is the loachs should turn it over pretty well anyway.