Marine & AlgaeBeginner🌗 Medium light

Gracilaria (red macroalgae)

Gracilaria sp. · also called Tang heaven, Red gracilaria, Ogo, Red ogo

🐾 Pet-safe

Generally non-toxic to cats and dogs.

Gracilaria is a branching red/maroon macroalgae prized both as a nutrient-export macro and as a nutritious live food for herbivorous fish like tangs (sold as "Tang Heaven"). It is hardy and grows in display tanks, refugiums, or tumble culture.

Educational only. KinStation content is reviewed by licensed veterinarians but cannot replace an in-person exam. Always consult a licensed veterinarian or board-certified specialist for diagnosis, treatment, or any decision affecting your pet's health.

Quick facts

Category	Marine & Algae
Family	Gracilariaceae
Native origin	Warm temperate and tropical coastal seas worldwide; widely cultivated (e.g. Hawaii) as 'ogo' and as an agar source
Care difficulty	Beginner
Light	Medium light
Pet toxicity	Pet-safe

Light

Medium aquarium lighting. As a red alga it does well under full-spectrum or slightly blue-shifted reef/refugium LEDs and does not demand extreme PAR; moderate light keeps the red coloration. Excess light plus low nutrients can pale it.

Water

Reef parameters: 22-26 C (72-79 F), salinity ~1.025 SG, pH 8.1-8.4, alkalinity 8-11 dKH. Consumes nitrate and phosphate for export. Tolerates a range of nutrient levels; iron and trace elements support deep red color and growth. No CO2 (marine).

Soil & potting

Not rooted. Either tumbled freely (like chaeto) in a refugium or wedged among rockwork in a display so fish can graze it. No substrate, root tabs, or aquasoil. Some forms attach loosely with a small holdfast but are typically grown unattached.

Environment — humidity, temperature, placement

Submersed only. No CO2. Moderate, gentle-to-medium flow keeps it clean and, if tumbled, rotating. Works in refugiums for nutrient export and in display tanks as a grazing pasture. Reverse-daylight photoperiod in a fuge helps stabilize pH.

Propagation

Spreads by simple vegetative growth and branching; pull or cut off a portion and place it in a new spot or tank to propagate. Fast regrowth after fish graze it makes it a sustainable live food crop.

Toxicity detail

Completely safe and in fact actively beneficial - one of the best vegetable foods for tangs, angelfish, and other herbivores, and reef-safe. Not invasive or regulated in aquarium use. No toxicity to shrimp or corals. (Note: some wild Gracilaria can bloom in eutrophic coastal waters, but this is not an aquarium concern.)

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

Gracilaria - Wikipedia (encyclopedia)
Gracilaria (Tang Heaven) Macroalgae - Reef2Reef (care guide)