CALCULATOR · CUC
Reef cleanup crew calculator
The short answer
A starting reef cleanup crew is roughly one grazing snail per 5 gallons, one Nassarius per 10, and one hermit crab per 10 — about 16 animals for a 40-gallon tank. Add them once the tank is cycled and showing algae, start light, and tune to what your algae and detritus actually need.
The ReefRig Cleanup Crew Method
Start light — roughly one grazing snail per 5 gallons, one Nassarius per 10, one hermit per 10 — then adjust to your algae. Half these numbers for a new tank.
A 40-gallon reef starts with about 8 grazing snails, 4 Nassarius and 4 hermits — roughly one cleaner per 2.5 gallons, tuned to algae.
Starter crew by tank size
Starting counts for an established, moderately-fed tank. Start at the low end and add more only if algae or detritus outpace the crew — an overstocked crew simply runs out of food.
| Display | Grazing snails | Nassarius | Hermits | Total |
|---|---|---|---|---|
| 10 gal | 2 | 1 | 1 | 4 |
| 20 gal | 4 | 2 | 2 | 8 |
| 30 gal | 6 | 3 | 3 | 12 |
| 40 gal | 8 | 4 | 4 | 16 |
| 55 gal | 11 | 6 | 6 | 23 |
| 75 gal | 15 | 8 | 8 | 31 |
| 90 gal | 18 | 9 | 9 | 36 |
| 120 gal | 24 | 12 | 12 | 48 |
| 180 gal | 36 | 18 | 18 | 72 |
What each cleaner does
| Animal | Job | Starting ratio |
|---|---|---|
| Grazing snails (Trochus / Astrea / Cerith) | Film & hair algae on glass and rock | 1 per 5 gal |
| Nassarius snails | Sand-bed detritus & leftover food | 1 per 10 gal |
| Hermit crabs (dwarf blue/red-leg) | Detritus & algae; keep spare shells | 1 per 10 gal |
Community-consensus starting ratios (BRS / Reef Cleaners / nano-reef guides) — a starting point to tune to your algae, not a stocking guarantee. Give hermit crabs a few spare empty shells in a range of sizes.
LIVE CALCULATOR
Build a starter crew
Enter your display volume for a starting crew. These are community-consensus starting counts to adjust to your algae — halve them for a brand-new tank.
Start at these numbers for an established tank and watch the glass and sand for a week. Add cleaners only if algae or detritus build up; halve the crew for a newly-cycled tank. These are starting counts, not survival promises.