Stocky Cerith Snail (Cerithium litteratum): Care and Diet

Lights go off, and an hour later you shine a flashlight into the tank. The glass right at the sand line, the strip you can never reach with a magnet, has a row of narrow spiral shells working along it. Those are ceriths, and that strip is one of the jobs they do better than anything else in the crew.

The stocky cerith, Cerithium litteratum, is a small, long-spired snail from the western Atlantic, Florida and the Caribbean. It lives on sand, seagrass and reef rubble in shallow water. It is part of our Florida Keys clean up crew field guide.

Quick facts

What a cerith eats

A cerith grazes film algae and diatoms, and it scavenges detritus and leftover food. AlgaeBarn describes ceriths as going after algal films first, then detritus, and also eating biofilms that other cleaners leave alone, including some cyanobacteria. In practice that makes a cerith a bridge between your glass grazers and your sand crew. It covers the bottom inch of glass, the rock that touches the sand and the top of the bed itself.

It does not eat hair algae and it will not clear a whole pane of glass the way a group of astreas will. Think of it as the crew member for the places in between.

How many cerith snails per gallon

Our clean up crew calculator adds stocky ceriths only when the tank has sand or mixed substrate and you report a dirty sand bed or detritus. It starts near one cerith per 7 gallons, then cuts that to about 70% for a tank two to six months old and to about 45% for a tank under two months. A bare-bottom tank gets none.

For an established tank that works out to six in a 40-gallon, eleven in a 75. AlgaeBarn suggests a heavier one per five gallons. We keep the count lower because ceriths share food with nassarius, conchs and hermits, and a starved crew is the most common way to lose snails. Add, watch for two weeks, and add more only if the sand line is still dirty.

Acclimation

Float the sealed bag for about 15 minutes to match temperature. Then drip tank water in slowly to match salinity, because invertebrates are sensitive to salinity swings. Never add the shipping water to your tank. Set each snail upright on the sand or rock.

Copper is toxic to snails. Never add one to a tank that has had copper in it.

Lifespan and size

SeaLifeBase and Reeflex both give a maximum shell length of about 1.3 inches. There is no published lifespan we trust. AlgaeBarn calls ceriths long-lived in captivity without giving a number.

AlgaeBarn notes that ceriths often breed once they settle into a healthy tank, but the eggs usually get eaten by other animals, so do not expect the population to grow on its own.

How we find them in the Florida Keys

Stocky ceriths live in shallow water on sand, seagrass and reef rubble, and they are most active at night. We collect them by hand under our Florida certificate and hold them in our Key West systems before they ship. Each shell is a wild shell, so pattern, wear and coralline cover vary from snail to snail.

Common problems and how to avoid them

• Hermit crabs want cerith shells. AlgaeBarn notes that empty cerith shells are popular and sometimes fought over, and Reeflex notes that small wild hermits move into them too. Keep spare empty shells in the tank so a hermit has another option.
• A cerith that hides all day is usually fine. They forage at night. Check with a flashlight after dark before you decide one is dead.
• A snail that stays upside down, smells bad or does not pull back when touched is dead or dying. Remove it before it fouls the water.
• Too many snails in a clean tank will starve. If the sand line stays spotless for weeks, you have enough ceriths. A sinking algae wafer at night can carry a small group through a lean stretch.

FAQ

The Underwater Gardener is a reef store in Key West, Florida. Our Florida Keys clean up crew is collected by our team under Florida certificate #AQ0254072 and conditioned in our Key West systems before it ships. Livestock ships UPS Next Day Air on Tuesdays and Wednesdays.