Cerith Snail
Cerithium spp.
The all-rounder cleanup snail — grazes algae on glass and rock, then burrows and stirs the sand.
Difficulty: BeginnerCleanup crewReef-safe
The cerith snail (Cerithium spp.) is the reef tank's all-rounder — a slim, pointed-shell snail that grazes film algae, diatoms and cyanobacteria off glass and rock, then burrows into the sand to eat detritus and leftover food while it oxygenates the bed. One snail doing three jobs makes it a cleanup-crew staple.
Care at a glance
| Adult size | Around 1 in. |
|---|---|
| Minimum tank | 10 gallons and up; stock roughly 1 per 3–5 gallons. |
| Temperature | 75–82°F (24–28°C). |
| pH | 8.1–8.4. |
| Specific gravity | 1.023–1.026 (reef-standard ≈35 ppt). |
| Other targets | Standard reef calcium and alkalinity keep the shell healthy; like all inverts it has zero tolerance for copper. |
| Diet | Detritus, uneaten food, fish waste, film algae, diatoms and cyanobacteria — on glass, rock and in the sand. |
| Temperament | Peaceful and fully reef-safe; active at night, often buried by day. |
| Reef-safe | Yes — won't touch corals; a pure grazer and scavenger. |
| Natural range | Wide-ranging (Indo-Pacific and Atlantic species). |
The fish store gets these wrong
Common myths, kindly corrected — no shame for having believed them.
- "A cerith only eats algae." It does more — it also scavenges detritus and leftover food and stirs the sand. That triple duty is why it's a staple.
- "It disappeared — it died." Usually it's just buried or grazing at night; ceriths are secretive by day.
Before you buy
- A cycled, established tank; drip-acclimate; never any copper.
- Some sand is a bonus (it burrows), though it also works glass and rock.
- Stock to your algae and detritus (~1 per 3–5 gallons).
Signs something's wrong
A struggling invert is usually telling you about water quality, acclimation, or (for shrimp and crabs) a fresh moult — here's what to watch for:
- Empty shell or a hermit wearing it — died, usually from an un-cycled tank, a swing, or copper.
- Never moving or grazing — check parameters.
Never
- Never add to an un-cycled tank.
- Never dose copper with inverts in the tank.
- Never drop them straight in — drip-acclimate.
Common cerith snail questions
What do cerith snails eat?
A bit of everything — film algae, diatoms and cyanobacteria on glass and rock, plus detritus and leftover food in the sand. They also burrow, which keeps the sand bed turned and oxygenated.
Are cerith snails reef-safe?
Completely — they're peaceful grazers and scavengers that won't harm corals or other inverts.
Why do my cerith snails hide during the day?
That's normal — ceriths are most active at night and often bury in the sand or tuck into the rock by day. You'll see them out grazing after lights-out.
How many cerith snails do I need?
Roughly one per 3–5 gallons is a sensible start, adjusted to how much algae and detritus your tank produces.
Do cerith snails eat cyanobacteria?
They graze it along with film algae and diatoms, which helps — but cyano is fundamentally a nutrient and flow problem, so fix those too.
Sources & further reading
This guide was written and fact-checked against these authorities. It's honest, general guidance — not a diagnosis, and not a substitute for an aquatic vet or your own test kit:
- Pod Your Reef — Saltwater Snails for Reef Tanks — roles, size, diet
- Fish Stores — Cerith Snail Care — size, tank, diet, acclimation
Written and fact-checked by The Coralkin Team against marine-aquarist sources — if your cerith snail is struggling, it's almost always water quality, acclimation or a moult — check those first and ask an experienced reefer. We never guess a care number.
🔬 Review status: team-written and fact-checked against cited sources · not yet reviewed by a marine vet. How we research & fact-check →