Berghia Nudibranch

Berghia stephanieae is the go-to biological control for Aiptasia — an obligate specialist that eats nothing else, so it is best treated as a temporary tool: it hunts cooperatively, breeds readily in the tank, and its population grows while Aiptasia lasts, then crashes and starves once the pest is gone, so plan to rehome survivors. It is one of the few genuinely captive-bred CUC species, non-aggressive and non-poisonous, and hides in rockwork by day to emerge and hunt at night. Endemic to the Florida Keys despite being widespread in the trade.