The Chocolate Chip Starfish, scientifically known as Protoreaster nodosus, is a prominent invertebrate in the marine aquarium trade, sought after for its distinctive appearance. This sea star possesses a body that is typically a light tan or reddish-brown color, strikingly contrasted by dark, conical tubercles or “knobs” covering its upper surface. These hard, black protrusions resemble chocolate chips, giving the animal its popular common name. Aquarists often inquire about its diet and whether it can coexist peacefully in a mixed-species habitat.
Identification and Natural Habitat
The Chocolate Chip Starfish has five thick, rigid arms and a robust central disk, growing up to 30 centimeters (12 inches) in diameter. The dark, pointed structures on its dorsal side serve a defensive purpose, potentially intimidating predators like triggerfish. It is classified within the class Asteroidea, making it a true sea star.
The natural range of Protoreaster nodosus spans the warm, shallow waters of the Indo-Pacific region, extending from Eastern Africa to the western Pacific Ocean. This species generally prefers soft substrates, such as sandy or muddy bottoms and seagrass beds, rather than the dense, hard structures of coral reefs. They are most commonly found in relatively shallow depths, typically ranging from 1 to 30 meters.
General Feeding Habits
In its native environment, the Chocolate Chip Starfish functions primarily as a detritivore and opportunistic scavenger, consuming fine organic matter. Field studies suggest that its diet mostly consists of microscopic organisms, including microbial and microalgal films (meiobenthos), which it grazes from the sand and seagrass. This establishes the star’s need for a continuous supply of small, nutrient-dense particles.
The sea star employs a unique method of feeding by everting its stomach, pushing it out through its mouth on the underside of its body. The stomach then envelops the food source, releasing digestive enzymes to break down the material externally. This process allows the star to consume items larger than its mouth opening, including sessile invertebrates and decaying matter. The star then retracts the stomach, bringing the partially digested meal with it.
Reef Tank Compatibility and Predation Targets
The Chocolate Chip Starfish is not considered reef-safe and is a known predator of sessile invertebrates, meaning it will eat coral. While its natural diet centers on microscopic films and detritus, the sea star is an opportunistic feeder that readily consumes corals and other immobile organisms in captivity, especially when preferred food sources are scarce. This predation results from the star seeking sufficient nutrition in an aquarium that cannot replicate the abundance of its natural food supply.
The star’s opportunistic nature makes it a threat to a variety of reef inhabitants. It preys on soft corals, such as gorgonians, and stony corals, including large-polyp stony (LPS) and small-polyp stony (SPS) varieties. Beyond corals, it targets sponges, clams and other bivalves, feather duster worms, and small anemones. Even clean-up crew members like snails and small urchins are vulnerable to the sea star’s predatory behavior.
The star may initially graze on detritus and leftover fish food, giving the impression that it is harmless. However, it will eventually seek out and consume soft-bodied, immobile prey, often resulting in the sudden disappearance of corals or clams. Because of this high risk of predation, the Chocolate Chip Starfish is only recommended for fish-only or aggressive tanks, where the loss of invertebrates is not a concern. Success with this species in captivity is often difficult, as many succumb to malnutrition when their dietary needs are not fully met.