CAEs don't usualy get along as they mature. They also don't make good tankmates for other fish and grow rather large at 10". I've never kept them with snails but I'd say you'd have more luck getting rid of snails with a botia such as the zebra loach though a CAE could probably eat smaller ones as well. If, on the other hand, you are worried about your pet apple snails, I doubt a CAE could eat those but it would be stressful for the snail to get nipped at or harassed constantly if the CAE did happen to take an interest.