Thorny oyster (Spondylus varius) care guide

Group
Other invertebrates
Other names
Variable thorny oyster, Spiny oyster, Spondylus delessertii, Spondylus striatospinosus
Family
Spondylidae
Origin
Indo-Pacific, including Australia, China, Japan, Taiwan and the Philippines; about 30 m
Water
saltwater
Maximum size
20 cm
Temperature
22–26°C
pH
8.1–8.4
Hardness
dKH 8–12, SG 1.023–1.025
Minimum tank
150 litres
Care level
expert
Temperament
peaceful
Reef safe
yes
Flow
Medium to strong

Care

Spondylus varius is the largest of the thorny or spiny oysters, reaching about 20 cm. Adult shells are white and often encrusted, with a crimson (sometimes yellow) tip at the hinge, and the mantle edge shows bright colours and rows of small eyes when open. In the trade, thorny oysters are usually sold just as Spondylus species, so the exact species is often uncertain. Tank set-up: a mature reef tank with medium to strong flow. It attaches firmly to rock or the tank floor and should not be moved once settled; place it where currents carry food past it. It is very sensitive to changes in salinity. It does not depend on light, but it often settles better in shaded spots. Quarantine is recommended to avoid introducing protozoan disease. Water: about 22–26 °C, pH 8.1–8.4, dKH 8–12 and specific gravity 1.023–1.025, with stable calcium and alkalinity. Feeding warning: filter feeders like this are hard to keep fed in home aquariums and many slowly starve over weeks or months, even in good reef tanks. Only buy one if you can feed it suitable fine foods every day, and check it is eating before you buy. Copper: copper-based medicines are toxic to shrimp, snails and most invertebrates, and some plant fertilisers carry copper too. Never treat a display tank holding this animal with copper; treat fish in a separate hospital tank, and drip-acclimatise new arrivals slowly. Sources: LiveAquaria (liveaquaria.com/products/thorny-oyster); Wikipedia (en.wikipedia.org/wiki/Spondylusvarius). Checked October 2026.

Diet

Filter feeder that eats plankton. Feed daily with phytoplankton, bacteria-based foods and fine particulate or dissolved organic foods (marine snow-type products), plus very fine zooplankton foods. Turn pumps down briefly when target-feeding near it.

Breeding

Sexes are separate in most Spondylus and they spawn into the water; larvae are planktonic. Not bred in aquariums.

Compatibility and tank mates

Reef safe and peaceful. Mantle-nipping fish such as angelfish, butterflyfish, puffers and triggers may stop it opening. Pyramidellid snails and some bristle worms and crabs can attack it. Keep away from stinging corals.

Last updated 8 October 2026. Community-edited care guide on Aquatic-Auctions.

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