Depending on what other type of fish you have, freshwater puffers are GREAT!!!! There are several types and they will wipe out ANY snail population in a short time. There is one that only gets about an inch or 2 long. Cute and they eat snails like thers no tomorrow!!! The only drawback is that they all can be a tad nippy to slow moving fish. I have a few in with my discus and they are fine.
There is a breed of dwarf puffer called a South American Puffer, which is freshwater, able to tolerate salt, 70-80 temp range, and generally very, very peaceful unlike the majority of its puffer kin (although some S.A.'s may nip fins at feeding time, many will not... watch their behavior before you buy). They are not schooling fish and can be kept 1 to a tank if desired, and they don't even seem to notice other fish (except for one week where the young puffer followed my guppies and pretended to be one!) S.A. Puffers will eat snails, and the vigorous ritual is very comforting for those who have had snail problems.
Tetraodon travancoricus the dwarf freshwater pufferfish is great and gets no larger than an inch.
Botia sidthimunki, the dwarf or chain loach, also stays rather small. These little fish are amazing and will keep you entertained for hours with their playful antics. They are really expensive though at thirty dollars each around here!
I just got 8 of the B. sidthimunki and they're really growing on me. I love Yo-Yo loaches, but they just get too big for my 20g. These little guys are just the right size, now all they need to do is eat all the snails.
Phil, you've made me seriously jealous. I've been looking for B. sidthimunki for several months, calling the LFSs within an hour's drive to check the order sheets on the days they put in their orders. Nothing on anyone's list so far. It took six months to find SAEs, and it may take that or more to find these.
Wonder if they might be in the Albany area. Anyone in the Capital district seen them? (NY, that is...)
Will loaches that eat the smaller pond snails bother bigger snails(apple etc) or shrimp? I'm thinking of my barred loaches and skunk botias. I'd like to get some shrimp but I'm worried that the loaches may bother them.
I introduced 2 zebra loaches today into my aquarium (My LFS only had 2, supposed to get me 2 more so I can have a little school of em). They are fairly small (supposedly don't get over 3 inches) and will eat snails. Cute guys too, great stripings, I can't wait to add 2 more next week.
Red tail Sharks are a great choice for getting rid of snails, they eat them as if there was no tomorrow, the only problem with those is that you have to get a pair, male / female because males are very aggressive toward other males.
Any boitia will eat anything that dwells the bottom of the tank including shrimp (bad experience)