What Is a Reef Tank Clean-Up Crew?

A clean-up crew (CUC) is a group of invertebrates that graze algae and detritus — astrea snails, cerith snails, nassarius for sand, hermit crabs in moderation. They reduce film algae and leftover food but do not replace water changes or lower nitrate alone.

Stock slowly. Ten snails in a new nano can starve once diatoms fade. Hermit crabs may pick at corals or each other if shells are scarce — offer spare shells.

Add CUC after the cycle, before or with your first fish depending on your plan. Note counts in ReefDiary so you remember when the last snail died — a CUC crash sometimes precedes an algae bloom.