Reef Cleanup Crew: What Eats What
🐠 The short version: a cleanup crew (CUC) grazes algae and scavenges detritus to keep a mature tank tidy — it’s support, not a cure. Mix grazers (snails that eat algae off rock) with scavengers (snails/hermits that eat leftovers on the sand). Stock it lightly — the old “one snail per gallon” rule just starves the crew. And never put copper anywhere near it.
🔧 Right-size your crew for your tank and problems with the cleanup-crew calculator — it uses modern per-animal rates, not the overstocking myth.
What a cleanup crew is (and isn’t)
A cleanup crew is a team of small invertebrates — snails, hermit crabs, and a few specialists — that grazes nuisance algae and scavenges uneaten food and detritus. In a mature, well-run tank it keeps glass, rock and sand tidy and helps hold nutrients down.
What it is not is a fix for bad husbandry. A CUC tidies a tank that’s already managed well; it can’t out-eat overfeeding, rescue an unstable tank, or cure an algae outbreak on its own. Think of it as the finishing crew, not the foundation.
Who eats what
Match the animal to the job — and remember a scavenger is not an algae-eater:
- Grazers (algae off rock & glass): trochus and similar snails work over film and nuisance algae; a trochus can also self-right if it topples. These are the workhorses.
- Scavengers (leftovers & detritus on/in the sand): nassarius snails are the classic sand scavengers (they surge up when food drops) but they don’t eat algae; hermit crabs scavenge detritus and some algae.
- Specialists: peppermint shrimp can help with aiptasia (not guaranteed, and they may nip corals if underfed); an emerald crab may eat bubble algae but turns predatory when hungry — keep it fed. Sand-sifting varies by species.
Browse the animals in the snails & crabs and shrimp hubs; each care sheet says exactly what it does and its honest caveats.
How many? Stock light, not by the gallon
The old “one snail per gallon” advice is a myth that leads to a crew that grazes the tank bare and then starves. Modern stocking is far lighter and job-based. The rule of thumb: start small, watch for two weeks, and add more only if there’s genuinely food for them. A new tank needs an even smaller crew than a mature one. The cleanup-crew calculator turns your tank size and problems (sand bed, bubble algae, aiptasia) into a sensible, right-sized crew rather than an overstock.
The two hard rules
- No copper, ever. Copper-based fish medications are lethal to every invertebrate and linger in rock and sand. Treat fish with copper only in a separate quarantine tank.
- Drip-acclimate slowly. Inverts are sensitive to salinity and pH shifts — drip them in and never pour shop water into the display.
A quick honest caveat on hermits
Hermit crabs are useful scavengers but can kill snails for their shells. Offer a few spare empty shells in the right sizes, keep hermit numbers modest, and pick reef-safe species. Prefer zero risk? Build the crew around snails and skip hermits.
The honest takeaway
A small, well-chosen cleanup crew — a few grazing snails, some sand scavengers, maybe a specialist for a specific pest — keeps a mature reef tidy. Stock it lightly, feed the tank (not the crew directly), keep copper away, and let it supplement your husbandry rather than replace it.
Sources & further reading
- Coralkin — Cleanup-crew calculator — modern, job-based stocking rates (not one-per-gallon).
- Coralkin — Snails & crabs and Shrimp hubs — who does what, with caveats.
- Coralkin — Beating reef tank algae & pests — where the crew fits in the bigger picture.
- Reef Cleaners, Top Shelf Aquatics & AlgaeBarn CUC guides (per our invert care sheets).
Common questions
What does a reef cleanup crew do?
It grazes film and nuisance algae and scavenges leftover food and detritus, keeping surfaces tidy in a mature tank. It is support for good husbandry, not a substitute - a cleanup crew tidies a well-run tank, it cannot fix an overfed or unstable one.
How many snails and hermits do I need?
Fewer than the old "one snail per gallon" myth suggests. Modern stocking is much lighter, because an overstocked crew simply starves once it has grazed the tank clean. Start small, watch for a couple of weeks, and add more only if there is genuinely food for them.
Whats the difference between grazers and scavengers?
Grazers (like trochus and other snails) eat algae off rock and glass; scavengers (like nassarius snails and hermit crabs) eat leftover food and detritus from the sand. A good crew mixes both so different jobs get covered - and note that a scavenger is not an algae-eater.
Can I use copper-based medication with a cleanup crew?
Never. Copper is lethal to snails, crabs, shrimp and all invertebrates, and it lingers in rock and sand. Keep any copper treatment in a separate quarantine tank, well away from your cleanup crew and corals.
Do hermit crabs kill snails?
They can - hermits sometimes kill snails for their shells. Provide a few spare empty shells of the right sizes to reduce it, keep hermit numbers modest, and choose reef-safe species. If you want zero risk, lean on snails and skip hermits.