Ask any group of aquarists their opinions on snails and you will receive a wide–and often emphatic–range of responses. Snails in aquaria can be highly beneficial, and equally problematical. Your opinion is probably influenced by the type of snails, and the kind of tanks you keep.
“Snails can be a lot of help,” says Charles Harrison. “Ramshorn snails help keep hydra and duckweed to a minimum, along with excess fish food.” Some aquarists are glad to have them, or pond snails, in their tanks.
Malaysian Trumpet Snails, however, tend to trigger controversy. They are fairly small creatures, reaching only about 3/4,” and have shells that look like tiny cornucopias or ice-cream cones. They are primarily active at night, so you will seldom see them. Considered useful by many, they prefer to burrow in the sand or gravel substrate, stirring it up nicely. They are beloved by plant folk, since they are carnivorous, and leave valuable plants alone unless extremely hungry.
For those with breeding tanks, egg predation by these snails can be a severe problem. Egg predation occurs either when the snail eats into the egg, releasing the contents, or consumes the entire egg. Most snails will eat eggs if given the chance; Malaysian Trumpet Snails will devour all the eggs they can find and everything else that is meaty and won’t swim out of reach. “Until the chorion firms up, the softest new eggs can be eaten by even small ramshorn snails,” points out Wright Huntley. “Pond snails can also eat very fresh eggs. But for real depredation, the … Malaysian Trumpet Snails are the most efficient egg eaters of all. I’ve never found eggs in a tank with Malaysian Trumpet Snails burrowing in the substrate.”
Additionally, if you are using powerheads or power filters, Malaysian snails will eventually get sucked into the impeller assembly and cause damage. “I have seen many of the impellers to filterheads and outside filters ruined by these critters,” says Al Anderson.
Some killikeepers keep Malaysian snails in their fry tanks and shoeboxes, finding that they are nearly indestructible. However, others point out that for indication of water problems, ramshorns are more effective and more desirable. The two species rarely live together, since the Malaysian snails eventually prey on the ramshorns.
One effective control measure for Malaysian snails is to remove the sand or gravel, scald it thoroughly to destroy the snails, then sift to remove the larger shells. To simply reduce the population, try placing an inverted saucer on the gravel in the evening. In the morning, it should contain a number of snails, which can then be removed and disposed of or relocated.
— G.C.K.A. Newsletter, July 1999