Free tool
Reef cleanup-crew calculator
Snails, hermits, a bubble-algae crab — how many does your tank actually need? Enter your volume and what you're dealing with, and we'll size a conservative crew. Forget "one snail per gallon" — overstock a cleanup crew and it starves.
- Start with this crew, then watch for two weeks. Still losing to algae? Add a few more — it's far easier than fixing a mass die-off from overstocking.
- A crew supplements good husbandry (nutrient export, feeding less, water changes) — it never replaces it. If algae keeps winning, the fix is usually nutrients, not more snails.
- Drip-acclimate every invert slowly, and never put copper in a tank with them.
Sources & method
- Grazing snails ~1 per 2–3 gal · nassarius ~1 per 3–4 gal · hermits ~1 per 5–10 gal · halve for new tanks — modern consensus (Top Shelf Aquatics, AllCorals).
- Species rates & behaviour from our own fact-checked care guides: trochus, nassarius, emerald crab, peppermint shrimp.
- The outdated "one snail per gallon" rule overstocks and starves the crew — skip it.
A free Coralkin tool — no sign-up, nothing saved. It sizes a sensible starting crew; your tank and your own eyes decide the rest. We never guess a care number.
Cleanup crew stocking rates
Modern reef consensus — halve the snail and hermit counts for a new tank (under ~6 months).
| Member | Job | Rate | When |
|---|---|---|---|
| Grazing snails (trochus) | Graze film algae, diatoms and cyanobacteria off glass and rock. | ~1 per 2–3 gal | Always |
| Nassarius snails | Sift the sand bed for leftover food and detritus (they do NOT eat algae). | ~1 per 3–4 gal | With a sand bed |
| Hermit crabs | Scavenge detritus and leftover food across the rockwork. | ~1 per 5–10 gal | Optional |
| Emerald crab | Eats bubble algae (Valonia) that snails and fish won't touch. | ~1 per 20–30 gal (max 3) | Only for bubble algae |
| Peppermint shrimp | Natural control for pest Aiptasia anemones. | a small group (2–6) | Only for Aiptasia |
Quick answers
How big a cleanup crew do I need?
Smaller than the old rules suggest — start conservative and add later. Modern reef consensus is roughly 1 grazing snail per 2–3 gallons, 1 nassarius per 3–4 gallons (only if you have a sand bed), and 1 hermit crab per 5–10 gallons if you want them. Halve the snail and hermit counts for a new tank (under ~6 months) because there's less for them to eat. Enter your volume and this tool sizes it for you.
How many snails per gallon for a reef tank?
Not one per gallon — that outdated rule overstocks the tank and starves the crew. Grazing snails like trochus go about 1 per 2–3 gallons, and sand-sifting nassarius about 1 per 3–4 gallons. Less is more: overstock a cleanup crew and it starves, so start small, watch for two weeks, and add a few more only if algae keeps winning.
What cleans up bubble algae or Aiptasia?
For bubble algae (Valonia) that snails and fish won't touch, an emerald crab is the natural control — about 1 per 20–30 gallons (max 3), and keep it fed, because a hungry emerald turns on corals and snails. For pest Aiptasia anemones, a small group of peppermint shrimp helps — but buy TRUE peppermints, since the humped-back camel shrimp is mis-sold as one and nips corals.
Will a cleanup crew fix an algae problem?
No — a cleanup crew supplements good husbandry, it never replaces it. If algae keeps winning, the fix is usually nutrients (nutrient export, feeding less, water changes), not more snails. Also drip-acclimate every invert slowly and never put copper in a tank with them.
Do hermit crabs belong in a cleanup crew?
They're optional and divisive. Hermits scavenge detritus and leftover food, but a hermit will kill a snail for its shell if it needs one — so add spare empty shells in several sizes and don't overstock. A sensible rate is about 1 per 5–10 gallons.