Black Longspine Urchin

Diadema-type urchins carry venom in those long black spines, which sounds alarming until you realize the real function is mostly defensive — the actual payoff for a reef keeper is one of the most thorough algae-grazing machines in the hobby, methodically working glass and rock clean overnight.

Care level: Easy · Temperament: Peaceful · Max size: ~4" body · Min tank: 30 gal · Reef safe: With caution (may knock over frags) · Diet: Herbivore, algae