Sea Lettuce

Ulva lactuca

Also known as Ulva, Green sea lettuce

SaltwaterMacroalgaeCuttings

Sea Lettuce (Ulva lactuca) — W.carter · CC0

Care at a glance

Light: High light
CO2: No CO₂ needed
Growth rate: Fast
Placement: Floating
Type: Macroalgae
Temperature: 72–81°F (22–27°C)
pH: 8.0–8.4
Max height: 9.8 in (25 cm)
Spread: 9.8 in (25 cm)
Nutrient uptake: Water column
Growth region: Submersed
Difficulty: Easy
Origin: Cosmopolitan; temperate and tropical coastlines worldwide
Family: Ulvaceae

Overview

One of the most aggressive nutrient exporters you can put in a refugium. Sea lettuce demands very intense full-spectrum light and nutrient-rich water; give it both and it pulls down nitrate and phosphate fast. Run it on a reverse photoperiod from the display to help buffer pH swings overnight. It is also a favorite live food, so trimmings can be fed directly to tangs, angels, and other herbivores. Harvest often, since removing biomass is what removes the nutrients.

In the wild

A bright green, semi-translucent sheet-forming seaweed of nutrient-rich temperate and tropical shorelines, where detached blades can grow into fragile sheets several feet across. It thrives in the kind of enriched water that would trouble a reef.

Good to know

Ulva lactuca is a green alga in the family Ulvaceae whose thallus is only two cells thick, giving it its thin, lettuce-leaf look. It has a complex life cycle that alternates between sexual and asexual generations, but in aquaria it mostly spreads asexually by blade fragments reattaching or by holdfast expansion.

Did you know

Sea lettuce is edible for people too and is the same genus eaten in seaweed salads, which is why herbivorous reef fish devour it so readily as a fresh green.