Green Lettuce Nudibranch

Green Lettuce Nudibranch: The Solar-Powered Algae Eater

The animal commonly referred to as the Green Lettuce Nudibranch is scientifically known as Elysia crispata (family Plakobranchidae, order Sacoglossa). It is a type of sea slug, but it is not a true nudibranch (which belong to the order Nudibranchia). This sea slug is one of the most popular and beneficial invertebrates for reef tanks due to its unique diet and appearance.

The Green Lettuce Nudibranch is instantly recognizable by the large, wavy, and folded tissue on its back called parapodia, which gives it a ruffled, lettuce-like appearance. It can range in color from pure green to vibrant hues of blue, white, and yellow. It typically reaches a size of 2 to 3 inches (5-7.5 cm) in a home aquarium.

What makes this sea slug truly remarkable is its ability to be "solar-powered." Through a process called kleptoplasty, it consumes algae and then steals the functional chloroplasts from the plant cells, incorporating them into its own tissues. These stolen chloroplasts continue to photosynthesize, providing the slug with supplemental energy from light, similar to how corals use zooxanthellae.

Diet & Compatibility:

• Diet: The Green Lettuce Nudibranch is a Specialist Herbivore. Its preferred food source is filamentous green algae, particularly the nuisance species Bryopsis and other macroalgae like Caulerpa and Halimeda. It consumes the algae by piercing the cell walls with a specialized tooth (radula) and sucking out the contents.
• Feeding Challenge: Despite its ability to photosynthesize, the slug requires a constant, reliable supply of algae to survive. If the algae population in the tank is depleted, the slug will starve and will not thrive on leftover fish food or prepared invertebrate pellets. Hobbyists must ensure an ample supply of its specific food is present, or be prepared to supplement with fresh macroalgae.
• Reef Compatibility: It is Completely Reef Safe. It will not eat or harm stony corals, soft corals, or other desirable invertebrates. Its dietary focus is strictly on algae.
• Temperament: It is Peaceful / Highly Delicate. It should only be housed with peaceful tankmates. Any predatory or nipping fish (e.g., Puffers, Triggerfish, larger Wrasses, large Angels) may harass or consume this soft-bodied slug.
• Vulnerability: Due to its soft body and benthic (bottom-dwelling) nature, the Green Lettuce Nudibranch is extremely susceptible to injury or death from strong pump intakes, overflows, and powerheads. All intakes must be securely screened with fine mesh or a sponge guard to prevent it from being sucked up. Like all invertebrates, it is also highly sensitive to fluctuations in salinity and water quality, as well as copper-based medications.

Quick Facts

• Scientific Name: Elysia crispata
• Primary Common Name: Green Lettuce Nudibranch (Sea Slug)
• Other Common Names: Lettuce Sea Slug, Solar-Powered Sea Slug
• Origin: Western Atlantic, Caribbean
• Max Size: 2-3 inches (5-7.5 cm)
• Temperament: Peaceful (Specialist Herbivore / Extremely Delicate)
• Diet: Specialist Herbivore (Feeds on Bryopsis and filamentous green algae)
• Minimum Tank Size: 20 Gallons
• Reef Compatibility: Completely Reef Safe