Will a Lettuce Sea Slug eat my corals?

No, they are strictly herbivorous and completely reef safe. They only possess specialized mouthparts designed to pierce and suck the sap out of soft filamentous algae.

Why did my Lettuce Sea Slug disappear into my filter?

Sea slugs are notorious for wandering into overflow boxes or powerheads. They have terrible eyesight and no understanding of mechanical flow. You must use foam sponges or mesh covers over all pump intakes to keep them safe.

Do they release toxins when they die?

Unlike sea apples or certain nudibranchs, Elysia crispata does not release a catastrophic toxin that will wipe out your aquarium if it dies. However, its decaying body will cause a small ammonia spike.

Why is my slug turning pale?

A pale Lettuce Sea Slug is usually a sign of either starvation or inadequate lighting. Without enough light or fresh algae to consume, the chloroplasts in their tissue begin to die off, causing them to lose their vibrant green and yellow hues.

Can I keep just one, or do they need friends?

They are completely solitary animals and do very well on their own. Keeping multiple slugs is only recommended if you have a very large aquarium with a massive, continuous supply of hair algae to support them.

MarineMarineIntermediate

Lettuce Sea Slug

Elysia crispata

The Lettuce Sea Slug is a fascinating, solar-powered sacoglossan prized by marine aquarists for its ability to consume nuisance hair algae.

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Ideal Conditions

Temperature: 22 – 27 °C
pH range: 8.1 – 8.4
Hardness: 14 – 22 dGH
Salinity: 1.023 – 1.026 SG
Adult size: 5 – 10 cm
Nano reef: 50 litres+
Lifespan: 1 – 2 years
Diet: herbivore
Water flow: low to moderate
Preferred setup: Mature reef with abundant macroalgae or hair algae

About the Lettuce Sea Slug

Often mistakenly called a nudibranch, the Lettuce Sea Slug (Elysia crispata) is actually a sacoglossan, a sap-sucking sea slug. It is renowned for its elaborate, highly ruffled parapodia (wing-like flaps) that run along its back, giving it the appearance of a curly lettuce leaf. These frills serve a remarkable biological purpose by increasing surface area for kleptoplasty—a process where the slug retains chloroplasts from the algae it eats. This allows the creature to photosynthesise and generate a portion of its own energy from aquarium lighting.

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Is it right for your tank?

Check Lettuce Sea Slug against a habitat you already keep. We compare water type, temperature, pH, adult size, group needs and everything living there.

Where Lettuce Sea Slug comes from

Native range

Caribbean Sea, Gulf of Mexico, Western Atlantic

Countries / regions

United States, Bahamas, Cuba, Jamaica, Mexico

Habitat

Shallow coral reefs, mangrove roots, and rocky areas with abundant sunlight and algal growth.

Commonly found in sunlit shallows where their preferred food, Bryopsis algae, thrives.

Similar species

Berghia Nudibranch
Berghia stephanieae
Sea Hare
Aplysia spp.
Velvet Nudibranch
Chelidonura varians

We’re adding more full species guides as the catalogue grows.

Compatible tank mates

Reviewed guidance based on this species' recorded traits.

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Ocellaris Clownfish
Amphiprion ocellaris
Peaceful fish that primarily occupy the water column and will completely ignore bottom-dwelling invertebrates.
Great
Trochus Snails
Trochus spp.
Harmless fellow herbivores that share the clean-up crew duties without outcompeting the slug for specific hair algae.
Great
Peppermint Shrimp
Lysmata wurdemanni
Generally peaceful but opportunistic; if underfed, some shrimp may pick at the delicate ruffles of the sea slug.
Compatible with caution
Sixline Wrasse
Pseudocheilinus hexataenia
Notorious for picking at and consuming small or delicate invertebrates, making the slow-moving slug an easy target.
Not recommended
Emerald Crab
Mithraculus sculptus
Opportunistic scavengers with strong claws that can accidentally or deliberately pinch and injure the soft-bodied slug.
Not recommended

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