Crabs

Tankmates: Reef-safety depends on species and size: avoid large hermits (Dardanus), arrow crabs with small fish/shrimp, and unidentified hitchhiker crabs. Hermits fight over shells. Emerald crabs may pick at corals when algae runs out. Large triggers, wrasses and puffers eat crabs.

Feeding: Emerald crabs eat bubble algae (Valonia); hermits graze film algae and detritus. Hungry crabs are more likely to turn predatory.