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Gold Ring Cowrie

Monetaria annulus

The Gold Ring Cowrie is a tireless nocturnal grazer, essential for controlling cyanobacteria and film algae. Completely reef-safe, it thrives in mature systems with abundant live rock.

Taxonomy

Class:Gastropoda

Order:Littorinimorpha

Family:Cypraeidae

Genus:Monetaria

Species:Monetaria annulus

Formerly known as:Cypraea annulus

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Water Temperature

22 - 28 °C

pH Value

8.1 - 8.4

Water type

Marine

Invertebrate type

Marine snail

Adult size

3 cm

Minimum group

>= 1

Ecological role

Herbivore

Species description

Geographical Origin and Habitat: Cypraea annulus (also known as Monetaria annulus) is a marine gastropod widely distributed throughout the tropical waters of the Indo-Pacific, from the East African coast and the Red Sea to Hawaii, Japan, and northern Australia. It inhabits shallow coral reefs, rocky intertidal zones, and tide pools, often found under stones or grazing on seagrass beds.

Taxonomy: Belongs to the class Gastropoda, family Cypraeidae, and genus Monetaria. It is commonly referred to as the Gold Ring Cowrie. While previously classified under the genus Cypraea, modern taxonomy places it in Monetaria. There are no major subspecies, though shell size and thickness vary by geographical temperature zones.

Social Behavior: It is a peaceful, nocturnal invertebrate that spends daylight hours hiding in dark crevices or under rock ledges, emerging at night to graze on exposed reef surfaces. It exhibits no territoriality or aggression toward other tank residents or members of its own species, making it an excellent utility animal.

Coloration and Sexual Dimorphism: The shell is smooth, egg-shaped, and glossy, with a pale greyish-blue to cream base color. Its defining feature is a prominent, bright golden-orange ring encircling the dorsal side of the shell. There is no visible sexual dimorphism; males and females are anatomically separate but look identical externally.

Care, breeding and tankmates

Tank Setup: Requires a mature marine aquarium of at least 50 to 100 liters (approx. 15-25 gallons) with plenty of established live rock. The rockwork must provide dark caves and shaded crevices for daytime shelter. Secure the rock structure firmly, as the cowrie can squeeze into tight gaps and potentially dislodge loose decor.

Diet and Feeding: A highly efficient herbivorous and detritivorous scavenger. It constantly scrapes biofilms, microalgae, film algae, and cyanobacteria (making it highly valued for controlling cyano outbreaks) off glass and rocks. In clean systems, supplement its diet with dried seaweed (nori) or spirulina-based pellets placed near its resting spots.

Water Quality: Maintain standard, stable marine parameters: temperature 24-27°C, pH 8.1-8.4, and specific gravity 1.023-1.025. It is extremely sensitive to copper-based medications, which are lethal to mollusks, and to elevated nitrates or sudden swings in water chemistry. Keep water clean and well-oxygenated.

Compatibility and Tankmates: Completely reef-safe; it will not bother corals, anemones, or other sessile invertebrates. Suitable for community reef setups with peaceful fish. Do not house with predatory species that feed on shelled mollusks, such as puffers, triggerfish, large wrasses, hermit crabs, or predatory sea stars.

Aquarium Breeding: Breeding in captivity is highly unlikely to succeed. They are dioecious, and females deposit adhesive egg capsules onto rocky surfaces, brooding them with their foot. The hatched larvae enter a long planktonic veliger phase, where they are typically skimmed out or consumed by filter feeders and fish.

Risks and Diseases: Starvation is the leading cause of death in small or overly sterile aquariums lacking algae. Shock from rapid salinity changes is also a major risk, making a slow drip-acclimation process of at least 1-2 hours essential when introducing this snail to a new aquarium.

Geographic Origin and Distribution

Cypraea annulus (also known as Monetaria annulus) is a marine gastropod widely distributed throughout the tropical waters of the Indo-Pacific, from the East African coast and the Red Sea to Hawaii, Japan, and northern Australia. It inhabits shallow coral reefs, rocky intertidal zones, and tide pools, often found under stones or grazing on seagrass beds.

Origin

Tropical oceans and reefsAfrica and MadagascarEast AsiaAustralia, New Guinea, and Oceania

Invertebrate profile

Diet: Herbivore
Ecological role: Herbivore
Shock sensitivity: Medium
Calcium and minerals: High
Molting: Shell growth
Reproduction: Oviparous
Compatibility & tankmates: Peaceful

Image gallery

Licensed images linked to the species or, when marked, to the closest representative taxon.

Related species

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Variants and close relatives

Same atlas type, nearby scientific identity, genus, or family.

Money Cowry

Monetaria moneta

Species description

Care, breeding and tankmates