Assasin snails have been known to prey on freshwater shrimp, especially if they start to drastically reduce the number of pest snails, as Bob Mehen explains…
Q: Are there any small- to medium-sized fish I can add to my 90cm community tank that will help deal with snails?
D. BURGESS, VIA EMAIL
A: Bob replies: Snails can sometimes become a nuisance in tanks, but usually this is the result of another problem. To reach ‘plague’ proportions they need to have a food source, and this is often provided by adding fish food in too great a quantity, the presence of dying plants in the tank, or infrequent maintenance — especially when it comes to syphoning of the substrate to keep it clean.
If you still have a problem with snails despite not overfeeding, adding another species of snail is actually one of the best solutions. The Assassin snail, Anentome helena, is a great solution. These are freshwater relatives of whelks and have pointed shells a couple of centimetres long, attractively marked with yellow and brown banding. Rather helpfully, they are a predatory species which love to feast on other snails.
Fish-wise, Clown loaches, Chromobotia macracanthus, often used to be recommended as snail eaters for aquariums but they grow far too large for most tanks at 30cm and need to be kept in groups of at least five, so they require a huge aquarium to properly thrive. However, their small cousin, the Dwarf chain loach, Ambastaia sidthimunki, would be a far better fit for your aquarium, with an adult size of around 6cm maximum. Again, like the Clowns they need to be kept in groups of at least five, so ensure you have enough space to add a suitably sized group. They will also eat snails, but good, regular maintenance is really the key to keeping snail populations in check.