Marine & AlgaeBeginner🌗 Medium light

Chaetomorpha (chaeto)

Chaetomorpha linum · also called Chaeto, Spaghetti algae, Chaeto algae

🐾 Pet-safe

Generally non-toxic to cats and dogs.

Chaetomorpha is the go-to refugium macroalgae for saltwater aquariums, forming a coarse, springy ball of stiff green filaments that strips nitrate and phosphate from the water. It is hardy, fast-growing, and does not go sexual (crash) the way Caulerpa can.

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Quick facts

Category	Marine & Algae
Family	Cladophoraceae
Native origin	Cosmopolitan in temperate and tropical seas worldwide; common in coastal lagoons and estuaries
Care difficulty	Beginner
Light	Medium light
Pet toxicity	Pet-safe

Light

Grows under a wide range of intensity. In a refugium it thrives under inexpensive full-spectrum or red/blue "grow" LEDs running 18-24 hours/day (commonly on a reverse-daylight photoperiod to stabilize pH). Brighter light = faster nutrient export. Roughly equivalent to medium aquarium lighting; not demanding on PAR.

Water

Standard reef parameters: temperature 22-27 C (72-80 F), salinity ~1.025 SG (35 ppt), pH 8.1-8.4, alkalinity 8-11 dKH. Tolerant of high nutrient loads (it is grown specifically to consume nitrate and phosphate). Benefits from trace iron dosing if growth stalls; do not over-dose. No CO2 needed (marine, supplied by carbonate alkalinity).

Soil & potting

Not rooted and not attached to substrate. The clump is left to tumble freely in a refugium so all sides receive light and flow, or wedged loosely against a baffle. No substrate, root tabs, or aquasoil required.

Environment — humidity, temperature, placement

Submersed only. CO2 not required. Placed in a refugium or sump (occasionally display) with moderate, turbulent flow to keep the ball rolling and free of detritus. Reverse-daylight lighting in the fuge buffers daytime/nighttime pH swings. Often used as a home for copepods and amphipods.

Propagation

Spreads simply by vegetative growth; pull off a handful and place it in another refugium to start a new culture. No special technique needed - just harvest excess to export nutrients. Does not rely on runners or spores in aquarium culture.

Toxicity detail

Completely safe to fish, corals, and invertebrates; shrimp and snails graze its surface and it shelters copepods. Not known to go sexual/asexual-crash like Caulerpa, so it will not nuke a tank. Not a regulated or invasive concern in aquarium use, though as a wild species it can bloom in nutrient-rich coastal waters.

Growth stages

How this plant changes through its life — each stage often has its own care, diet and space needs.

Photo coming soon

Spore / recruit

Aquatic plants and macroalgae establish from spores, seeds, or drifting fragments that settle and attach to substrate or rock. Many freshwater aquarium plants and marine macroalgae also spread readily from a detached piece that takes root or holdfast.

Photo coming soon

Young growth

Young growth puts out its first blades, fronds, or leaves and anchors with roots or a holdfast. Submersed plants may look different from their emersed form, and growth speeds up as the plant adapts to the water's light and nutrients.

Mature

A mature aquatic plant or macroalga reaches its full size and characteristic shape, forming the dense growth, runners, or fronds typical of the species. Established plants spread to fill space and can be divided or trimmed to propagate.

Sources

Chaetomorpha - Wikipedia (encyclopedia)
Chaetomorpha Macroalgae Refugium Guide - Reef2Reef (care guide)