Sea Hare

Aplysia californica

Identification	Large, soft-bodied sea slug with a mottled brown to greenish body and two prominent ear-like rhinophores on the head that give it a rabbit-like appearance — hence the name. Parapodia (wing-like flaps) along the sides can be used for swimming.
Maximum Size	Up to 16 inches (40 cm); typically 5–8 inches in aquarium
Origin	Eastern Pacific — California to Baja California; various species across Indo-Pacific
Minimum Tank Size	30 gallons
Reef Compatible	With caution — see Cautions

Behavior

Sea hares are exceptional algae consumers, particularly effective against nuisance hair algae, Bryopsis, and Caulerpa — often considered one of the best biological controls for these pest algae. Slow-moving and peaceful. When stressed, can release a purple ink as a defense mechanism.

Diet & Feeding

Herbivore. Consumes large quantities of nuisance algae including hair algae, Bryopsis, and Caulerpa. Once the algae is under control, may starve — have a plan to rehome or feed dried seaweed.

Cautions

When stressed or dying, releases a mucus/ink that can be toxic to tank inhabitants and may crash oxygen levels in a small tank. Remove immediately if it looks stressed, pale, or inactive. Short-term addition for algae control is the most practical approach.