Orange Line Urchin - Tripenustes gratilla

Orange Line Urchin (Tripneustes gratilla)

The Orange Line Urchin, Tripneustes gratilla, is a colourful marine grazing urchin with a rounded body, short spines and attractive contrasting lines or bands that may appear orange, white, purple, black or brown depending on the individual. Also known as the Collector Urchin, Halloween Urchin or Sea Egg Urchin, this Indo-Pacific echinoderm is valued in mature reef aquariums for grazing algae and natural surface films. It is generally reef safe, but it may carry loose items on its body and can bulldoze unsecured frags while moving around the aquarium.

Common Name:
Orange Line Urchin, Collector Urchin, Halloween Urchin, Sea Egg Urchin, Variegated Sea Urchin.

Scientific Name (Latin):
Tripneustes gratilla

Maximum Size:
Usually around 10–15 cm across including spines, with aquarium specimens often sold smaller.

Water Type:
Marine

Origin / Natural Habitat:
Tropical Indo-Pacific and other warm marine regions, including the Red Sea, Indian Ocean, Pacific reef regions and Hawaii. Naturally found in shallow seagrass beds, reef lagoons, coral rubble, reef flats and coral reef areas, usually from the intertidal or shallow subtidal zone down to around 30 m.

Water Parameters:
Temperature: 24–27°C
pH Range: 8.1–8.4
Hardness or Salinity: SG 1.023–1.025

Temperament:
Peaceful. It will not attack fish, corals or mobile invertebrates, but it may dislodge loose coral frags, carry small objects, or move lightweight decorations as it grazes. It should not be kept with urchin-eating predators such as triggers, puffers, large wrasses, some crabs or harlequin shrimp.

Diet:
Herbivorous to omnivorous grazer. In nature, Tripneustes gratilla feeds mainly on macroalgae, seagrass, diatoms, algal films and other natural surface growth, with some sources also noting coral tissue scraped from rock surfaces and small organic material. In the aquarium, it grazes film algae, green algae, turf algae and biofilm from rockwork and glass. In very clean systems, supplement with dried seaweed, nori, algae wafers or suitable marine herbivore foods placed near the urchin.

Minimum Tank Size:
A minimum of 200 litres is recommended for a single specimen, with larger mature aquariums preferred. The key requirement is a stable system with enough established grazing surface and supplemental feeding if natural algae is limited.

Behaviour & Activity:
A slow-moving reef grazer that travels over rockwork, glass, rubble and sometimes sand while scraping algae and surface films. Like other collector-type urchins, it may attach small shells, algae, rubble, coral fragments or debris to its body for camouflage and protection. It may be more active during quieter periods or at night, although settled specimens often graze throughout the day.

Reef Safe:
Reef Safe
Generally safe with corals, snails, hermit crabs, cleaner shrimps and peaceful reef fish. It does not actively prey on typical reef livestock, but it can knock over or carry unsecured coral frags and may graze some coralline algae or delicate surface growths. Secure frags and loose pieces before adding this urchin.

Special Requirements or Care Notes:
Requires stable salinity, good water quality and slow acclimation. Like other echinoderms, it is sensitive to copper, sudden salinity changes, poor acclimation and high nitrate levels. Do not add to a new, sterile aquarium with little algae growth. Spine loss, poor grip or inactivity can indicate stress, starvation or declining water quality. Provide supplemental seaweed if the aquarium is very clean, and protect it from predatory fish or crabs.

Suitable for:
Beginner to intermediate fishkeepers

Availability:
Occasional in trade / Captive-bred or aquacultured where relevant

All images are a visual representation of the animal you will receive, made to be as accurate as possible. Please note that Mother Nature is a wonderful thing, and variation in patterns and colours will occur — that is part of the unique beauty of these animals.