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
Temperature: 72–81°F; 22–27°C
Max height: 9.8 in; 25 cm

Growth rate: Fast
Placement: Floating
Type: Macroalgae
pH: 8.0–8.4
Spread: 9.8 in (25 cm)
Nutrient uptake: Water column
Growth region: Submersed
Difficulty: Easy
Family: Ulvaceae
Origin: Cosmopolitan; temperate and tropical coastlines worldwide

Overview

Sea Lettuce is an easy, fast-growing green macroalga for a saltwater refugium. It is one of the most aggressive nutrient exporters you can put there.

Did you know

Sea Lettuce is edible for people too. Its genus, Ulva, is the one eaten in seaweed salads.

Caring for Sea Lettuce

Let Sea Lettuce float free in a refugium. Give it very intense, full-spectrum light and nutrient-rich water, and it pulls down nitrate and phosphate fast. It needs no added CO2. Run it on a reverse photoperiod from the display to help buffer pH swings overnight.

Keep the water at 72 to 81°F (22 to 27°C) with a pH of 8 to 8.4. Sea Lettuce grows fast, so harvest it often, since removing biomass is what removes the nutrients.

Feed the trimmings straight to tangs, angels and other herbivores, which devour it as a fresh green. Any piece cut off grows into a new plant. In the tank it spreads mostly by blade fragments reattaching or by its holdfast expanding.

Good to know

Sea Lettuce, Ulva lactuca, is a green alga in the family Ulvaceae. Its thallus is only two cells thick, which gives it the thin look of a lettuce leaf. Its life cycle is complex, alternating between sexual and asexual generations.

In the wild

Sea Lettuce is a bright green, semi-translucent seaweed that forms sheets along temperate and tropical shorelines worldwide. It does well in nutrient-rich water, the kind of enriched water that would trouble a reef. Detached blades can grow into fragile sheets several feet across.