Lettuce sea slug (Elysia crispata) care guide

Group
Other invertebrates
Other names
Lettuce nudibranch, Lettuce slug, Tridachia crispata, Elysia clarki
Family
Plakobranchidae
Origin
Tropical western Atlantic and Caribbean; shallow, clear reef areas
Water
saltwater
Maximum size
5 cm
Temperature
22–26°C
pH
8.1–8.4
Hardness
dKH 8–12, SG 1.023–1.025
Care level
intermediate
Temperament
peaceful
Reef safe
yes

Care

The lettuce sea slug is a Caribbean sea slug up to about 5 cm long, named for the very frilly, ruffled flaps along its back that look like a lettuce leaf. Most are green, but some are blue, pale with red or yellow lines, or brownish. It is often sold as a 'lettuce nudibranch', but it is a sacoglossan (sap-sucking sea slug), not a true nudibranch. LiveAquaria sells lettuce slugs as Elysia species from both the Caribbean and the Indo-Pacific, so not every 'lettuce slug' is this species. It is one of the 'solar-powered' sea slugs: it keeps the chloroplasts from the algae it eats alive in its own cells, where they go on photosynthesising for about 40 days and feeding the slug. Adults rely on this more than juveniles. Keep it in a mature reef tank with plenty of live rock and algae to graze, good light and room to forage. Screen pump intakes and overflows, which can kill it. It is sensitive to high nitrate and copper. The biggest problem is food: it eats only certain green algae, and in a clean tank it slowly starves. Many keepers buy it hoping it will clear Bryopsis; it may graze some soft green algae, but this is not reliable and our sources do not confirm it eats Bryopsis. Copper-based medicines and some plant fertilisers are toxic to shrimp, snails and most invertebrates. Sources: LiveAquaria (liveaquaria.com/products/lettuce-sea-slug); Wikipedia (en.wikipedia.org/wiki/Elysiacrispata). Checked October 2026.

Diet

A herbivore that pierces green algae and sucks out the contents, keeping the chloroplasts. Recorded foods include Caulerpa species, Halimeda, Penicillus and Vaucheria; its main natural food is not well known. In the aquarium it grazes algae on live rock and also gets energy from photosynthesis, so it needs good light as well as algae. It will not take prepared foods and is likely to starve in a tank with little green algae.

Breeding

Sea slugs are hermaphrodites; mating in this species is poorly known and individuals cannot be told apart. Egg masses are laid on flat, upright algae and the embryos develop in about 15 days. Some young change into crawling slugs inside the egg capsule and stay near the parent, while others hatch as swimming larvae and settle elsewhere. Eggs sometimes appear in aquaria, but raising the young is rarely successful.

Compatibility and tank mates

Reef safe and harmless to corals, fish and other invertebrates. Vulnerable to pumps and overflows, and may be picked at by puffers, triggers, some wrasses and crabs. Does not compete well with large numbers of other algae grazers.

Last updated 8 October 2026. Community-edited care guide on Aquatic-Auctions.

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