Red knobbed starfish

Geographical Origin and Habitat: This species is native to the western Indian Ocean, widely distributed along the coast of East Africa (including Kenya, Tanzania, and Mozambique), Madagascar, the Seychelles, India, Sri Lanka, and parts of Western Australia. It inhabits shallow sandy or muddy seabeds, seagrass meadows, and rocky reefs at depths from 1 to 100 meters.

Taxonomy: Belonging to the phylum Echinodermata, class Asteroidea, order Valvatida, and family Oreasteridae. Originally described within the genus Protoreaster, it features a heavy skeleton composed of calcareous ossicles. It can grow to a maximum diameter of approximately 30 cm (12 inches). It typically possesses five thick arms, though anomalies occur.

Social Behavior: It is a solitary species, active during both day and night. It is a carnivorous predator and opportunistic scavenger that crawls slowly over the substrate searching for food. For defense, it relies on its hard, pointed tubercles and natural skin toxins. It is not suitable for reef tanks containing corals or small delicate invertebrates.

Coloration and Sexual Dimorphism: The coloration is spectacular and distinctive. The body has a light gray, cream, or whitish base color, adorned with a grid-like network of red or orange lines. Along the center and margins of the arms, it features large, prominent, bright red or orange knob-like tubercles (spines) that project upward.

Tank Setup: Requires a large, well-established marine aquarium of at least 300 liters (approx. 80 gallons). The setup must include extensive open sandy areas for the starfish to glide over, combined with stable, secure live rock structures for climbing. Avoid cluttered aquascapes that could restrict the animal's movement.

Diet and Feeding: It has no specific lighting requirements, but a standard light cycle is recommended to support substrate microflora. The water temperature must be kept stable between 23°C and 26°C (73-79°F) using a reliable heater with a thermostat. Avoid rapid temperature drops, which can cause severe stress.

Water Quality: Water quality must be excellent and highly stable. Salinity is a critical parameter and must be kept constant at a specific gravity of 1.023-1.025. This species is extremely sensitive to rapid changes in specific gravity, elevated nitrates, phosphates, and copper-based medications, which can be rapidly fatal.

Compatibility and Tankmates: A voracious carnivore and scavenger. It cannot survive on detritus alone; it must be actively fed 2-3 times a week by placing small pieces of meaty foods directly underneath its body, such as fresh shrimp, clams, mussels, squid, or fish. Without target feeding, it will quickly starve and waste away.

Aquarium Breeding: Strictly not reef-safe. This starfish will actively consume soft corals, zoanthids, sponges, anemones, clams, oysters, snails, and even other starfish. It can only be housed in fish-only-with-live-rock (FOWLR) aquariums alongside moderately sized, non-aggressive fish species.

Risks and Diseases: The primary risk is osmotic shock during introduction; it requires a very slow and meticulous drip acclimation (lasting at least 2 hours). Signs of poor health include loss of color, body softening, or white necrotic patches on the skin. Never expose the starfish to the air during transfers.