Ulva sp.
| Care Level | Easy |
| Lighting | Moderate to high |
| Water Flow | Moderate to strong |
| Placement | Refugium or display, on rock |
| Primary Use | Nutrient export & herbivore food |
| Growth Rate | Fast |
Overview
Sea Lettuce (Ulva) is a bright green macroalgae that grows in thin, translucent, lettuce-like sheets. It is a fast-growing, hard-working nutrient exporter for the refugium and one of the best natural foods for tangs, angels, and other herbivores — many keepers grow it specifically to feed the tank. It works equally well as a splash of green in the display.
Care & Placement
Easy. Give it moderate to high light and moderate to strong flow so the fronds tumble and get light on all sides, in a refugium or wedged into display rock. As it takes up nitrate and phosphate, harvest a portion regularly — that is how the nutrients actually leave the system. It thrives on the same nutrients you are trying to reduce.
Uses & Nutrient Export
Two jobs: it pulls nitrate and phosphate out of the water as it grows (harvest and discard some to export those nutrients), and it is a premium herbivore food — clip a piece to a veggie clip or let fish graze it directly. It is a healthier, more natural green than dried sheet algae.
Propagation & Harvesting
Effectively self-propagating: it grows fast, so you simply pull out and discard (or feed) the excess to keep it in check and export nutrients, keeping a portion to regrow. Light plus nutrients is all it needs.
Cautions
It grows fast, so it can spread if left unmanaged — harvest regularly. Give it strong enough flow and light or lower fronds can die back and foul. It lacks the notorious sexual-event crash of Caulerpa, but any macroalgae removed all at once can affect water quality, so harvest gradually.
Frequently Asked Questions
Is Sea Lettuce good for nutrient export?
Yes — Ulva is a fast grower that readily absorbs nitrate and phosphate. Grow it in a lit refugium and harvest a portion regularly; removing that growth is what exports the nutrients.
Can I feed Sea Lettuce to my fish?
Absolutely. It is one of the best natural greens for tangs, angelfish, and other herbivores — clip it in the tank or let them graze it in the refugium.
Does Sea Lettuce grow fast?
Very. With moderate-to-high light and good flow it grows quickly, which makes it excellent for nutrient export and feeding, but it also means you should harvest it regularly.