Ulva intestinalis Care Guide
Ulva intestinalis is a tubular green seaweed (gutweed) tolerant of variable salinity, useful in tide-pool, marine and brackish setups.
Compiled by Aquairi from published sources · Published · Updated
Overview
Ulva intestinalis is a green seaweed of the family Ulvaceae, also known as gutweed or grass kelp. Its thallus is completely tubular and inflated, expanding toward the middle and forming intestine-like strands. Formerly placed in the genus Enteromorpha (as Enteromorpha intestinalis), it was moved into Ulva following genetic analysis in the early 2000s.
Taxonomy
- Family: Ulvaceae
- Genus: Ulva
- Scientific name: Ulva intestinalis
- Class: Ulvophyceae; Order: Ulvales
- Common synonym: Enteromorpha intestinalis
Habitat
The species is cosmopolitan, recorded across the Bering Sea, North Pacific, Atlantic, Baltic and Mediterranean and around New Zealand. It grows on rocks and in rock pools and tolerates a wide range of salinity, which makes it common in brackish and tide-pool environments.
Tank requirements
- Water type: saltwater / brackish tolerant
- Temperature: 12-28 °C (54-82 °F)
- pH: 7.5-8.4
- GH reference: 4-14 °dGH
- Lighting: high
- CO2 injection: not required
- Growth rate: fast; fronds up to ~30 cm
Care and propagation
Ulva intestinalis grows quickly under bright light and spreads readily, so regular harvesting controls the biomass. It reproduces through an alternation of generations in which gametophyte and sporophyte are isomorphic, and it can reproduce throughout the year. Periodic trimming, roughly every two weeks, keeps growth manageable.
Ecology
Because the species responds strongly to nutrients, it can proliferate in nutrient-rich waters. This same trait is exploited in aquaria, where it helps absorb dissolved nutrients and can serve as a food source for herbivorous animals.
Propagating Ulva intestinalis (Gutweed) in Marine Refugiums
Overview
Ulva intestinalis, commonly called gutweed, is a green macroalga whose branched fronds are completely tubular, expanding in width toward the mid-thallus and reaching 15 cm or more in length. Cells are irregularly arranged and carry hood-shaped chloroplasts, typically with a single pyrenoid. It is a cosmopolitan species found across temperate and polar regions and tolerates variable salinity, which makes it well suited to marine, tide-pool, and brackish setups.
In an aquarium it grows fast and exports nitrogen and phosphorus quickly, while the soft tubular sheets are readily grazed by tangs and other herbivores. Because the species reproduces throughout the year and follows an alternation of generations with isomorphic gametophyte and sporophyte stages, you can multiply your stock easily by simple division.
Propagation Method
Gutweed is propagated vegetatively by dividing or tearing the thallus. Each separated piece of tubular frond continues to photosynthesize and elongate on its own, so there is no need for cuttings rooted into substrate. Free-floating clumps tumbled in a refugium grow readily without anchoring.
Step-by-Step
- Select a healthy, bright-green clump with firm, inflated tubular fronds.
- Gently tear or cut the thallus into several pieces, each a few centimeters across.
- Place the divisions in a well-lit refugium or grow-out area with gentle flow.
- Let pieces tumble freely or rest loosely; no substrate anchoring is required.
- Within days the fragments resume rapid elongation and thicken into new clumps.
Conditions for Healthy Growth
- Strong lighting to drive the high growth rate typical of this species.
- Stable marine to brackish salinity; the species tolerates variable salinity well.
- Temperate-friendly temperatures, reflecting its worldwide temperate and polar range.
- A steady supply of nitrogen and phosphorus, which the alga rapidly takes up.
- Gentle, continuous water movement to keep clumps tumbling and evenly lit.
Maintenance
Harvest and thin the colony on a regular cycle. Removing a portion of biomass physically exports the absorbed nitrogen and phosphorus from the system, and the trimmings make excellent fresh food for tangs and other grazers. Frequent thinning also keeps the fast-growing mat from shading itself.