Snails and Fish: Which Combinations Work
Loaches, pufferfish and some cichlids eat snails, and assassin snails hunt other snails. Nerites suit planted tanks; apple snails eat plants; assassins take shrimplets.
Most aquarium snails can live alongside peaceful community fish, but loaches, pufferfish and some cichlids eat snails, and the assassin snail (Anentome helena) preys on other snails. For planted and shrimp tanks, nerite snails are the group the sources describe as leaving plants alone and not breeding in fresh water, while assassin snails and apple snails are the main poor fits.
Fish that eat snails
Seriously Fish lists aquatic molluscs as part of the natural diet of the clown loach (Chromobotia macracanthus) and notes that it will eat both snails and shrimp. It gives the same verdict for the zebra loach (Botia striata): both species prey on snails, but neither is an obligate molluscivore, so neither should be bought as the answer to a snail infestation. The clown loach also reaches 400 mm standard length, should be kept in a group of at least 5–6 and preferably 10 or more, and needs a tank with base measurements of at least 180 × 60 cm, which rules it out for most home aquariums. Practical Fishkeeping (PFK) describes the dwarf chain loach (Ambastaia sidthimunki) as a much smaller snail eater of about 6 cm that should be kept in a group of ten or more.
PFK describes many pufferfish as snail eaters with beak-like teeth for crushing shells, but also as aggressive toward tank mates and shrimp. For the pea puffer (Carinotetraodon travancoricus), at about 25 mm the smallest puffer, Seriously Fish advises feeding small snails with their shells on regularly, because its teeth grow continuously and must be worn down. The same profile says it nips the fins of slow-moving or long-finned fish and is not usually recommended for community tanks. In a puffer tank, snails are food rather than tank mates.
Among cichlids, PFK names Anomalochromis and the convict cichlid as snail eaters. In Lake Malawi, Trematocranus placodon, a cichlid of up to 25 cm total length, feeds mainly on aquatic snails, according to Wikipedia.
Assassin snails and other snails
Anentome helena is a carnivorous snail that feeds on worms and other gastropods and often buries itself in the substrate to ambush prey. Wikipedia notes that it is used to control small pest snails such as the Malaysian trumpet snail. Because it preys on gastropods in general, the sources give no basis for assuming it will spare snails the owner wants to keep. Unlike many pest snails, the sexes are separate; females lay single eggs in clear, square capsules that usually hatch within a few weeks. PFK warns that assassin snails keep breeding if overfeeding continues, and that they have been known to eat shrimplets.
Snails for planted tanks
- Nerites (Neritina natalensis, listed on Wikipedia as Vittina natalensis): an algae-eating snail of about 2.5 cm, kept at 22–26 °C. It reproduces only in brackish or salt water, so its numbers do not increase in a freshwater tank. Tropical Fish Hobbyist (TFH) says nerites tend not to bother plants but leave small egg capsules on hard surfaces.
- Ramshorn and bladder snails (Physella acuta): TFH says they breed enough to help keep algae down and graze over glass, decor and plants. PFK lists them among the usual nuisance species, which breed prolifically when the tank holds excess organic waste.
- Malaysian trumpet snail (Melanoides tuberculata): a nocturnal burrower that eats microalgae and detritus, and PFK says it helps aerate the substrate. Females are parthenogenetic and brood live young, and Wikipedia notes that the hobby is divided over whether it is a pest or a useful cleaner.
- Apple or mystery snails (Pomacea): TFH says they eat desirable plants and would not use them in a planted tank. Wikipedia describes adult Pomacea canaliculata as feeding on floating and submerged plants. Pomacea bridgesii lays its egg clutches above the water line, and a single clutch can produce up to about 200 young.
Snails in shrimp tanks
The main conflict in a shrimp tank is the assassin snail: PFK states it is not suitable where shrimps are being bred because it eats shrimplets. Nerites are a predictable choice because they cannot multiply in fresh water. Ramshorn and bladder snails will multiply as far as the available food allows. The snail-eating fish above are a separate risk: Seriously Fish notes that clown loaches eat shrimp, and PFK describes puffers in general as aggressive toward shrimp. Fish choices for shrimp are covered in the shrimp-and-fish-compatibility-guide.