Marine snails in the wild populate reefs and ocean floors, ranging from 1/2 an inch to a whopping 20 inches in diameter. These beautiful invertebrates are a great addition to many saltwater tanks, but it's important to know the diet of your adorable new gastropod before introducing him to your other aquatic livestock. While most marine snails -- also known as sea snails or saltwater snails -- are herbivores, some prefer to hunt or scavenge prey from their surroundings. These carnivores can make quick work of eliminating defenseless species in a tank.
By nature, snails are scavengers; carnivores and herbivores alike. They tend to feed on decaying plant matter, organic waste such as fish excrement, molts and dead fish, uneaten fish food and algae. Some can sift through rocks, glass and even sand to pull out and consume every tiny bit of organic matter, and they can do it without harming the other inhabitants of the tank. These omnivores are known as detritus-eaters: Detritus is another word for waste or debris.
Some omnivores are "suspension-feeders," and strain food particles of all types from the water that surrounds them.
Lending a Helping Tongue
Appreciating the greener things in life, the herbivorous saltwater snail is a gentle and peaceful creature. They spend their days gliding about the tank on their one foot, eating algae in a fascinating manner. Marine snails use their raspy tongue, called a "radula" to lick across the surface of the algae. The rasps of the tongue scrape away algae from the sides of the tank, hidden nooks and crannies, and even from the shells of other snails.
An added benefit to snails over other algae eaters such as crabs, is that they carefully munch away at algae that clings to reef systems without harming the coral. The dark brown Cerith snail, for example, is so good at nibbling at hair algae that he can gulp down the diatoms, or infinitesimal single cells at the root of this aquarium pest. Through this method, one hungry snail can eventually rid an entire aquarium from this nuisance.
If your new star performer has eaten all of the visible algae in the tank, commercial algae discs, sheets of dried seaweed or blanched vegetables -- lettuces, zucchini and broccoli are great -- will tide him over in the meantime.
It Came from Beneath the Sea
Carnivorous snails are interesting, yet deadly, and should be carefully housed with other inhabitants that won't become the snail's next meal. They have a variety of hunting patters, including hiding in underground burrows, or smothering victims with their slimy feet or drilling into the shells of bivalves such as clams. They eat worms, slow-moving fish, sea slugs and even members of their own species.
Predatory marine snails found in aquarium shops and suppliers are not dangerous to humans. If you capture your own livestock for your tank, however, you must be well-informed of the animals you add. Cone snails look beautiful with their remarkable shells, however these gastropods are one of the most venomous creatures in the world. They can quickly cause a reaction that ranges from a very bad bee sting to death.
A handy way to identify if your marine snail is an herbivore or carnivore is to look at the end of its shell. The back of the shell scoops away to allow the hind part of the snail through is known as the "siphonal notch." If this notch is indented, causing a C-shape in the end of the shell, then the snail is most likely carnivorous. Just remember: "C" for carnivore.