The starfish diet evades generalization. Some starfhsi are scavengers, some specialize on certain prey species and others consume any living creature they can capture. Experienced aquarists can successfully maintain starfish in captivity, as long as they thoroughly research the creatures' needs and accommodate them. While algae eaters will help themselves to the algae growing in the tank, carnivorous species will require several weekly meals of fish, mussels or clams. A variety of factors determine how much or how often to feed.
Starfish are invertebrates, specifically echinoderms, who live throughout the warm, shallow oceans of the world. Starfish carry most of their internal organs in the central disc region. Their mouths are on the underside of their discs. Some species evert their stomachs to engulf their prey before bringing it back into the body cavity. Starfish have evolved a number of other unusual traits, including the power of regeneration: They often replace arms lost in encounters with predators.
Many of the sea star species best suited to aquarium life are scavengers wh consume algae, detritus and small organism. Brittle sea stars (Ophiure protoreaster) are omnivores who consume a variety of foods in the wild; in captivity, you can feed them zooplankton, liquid invertebrate food or finely chopped fish. Serpent sea stars (Ophiomyxa ssp.) are more carnivorous -- place finely chopped fish, mussels or meat, near or under their disc at feeding time. Crown-of-thorns starfish (Acanthaster planci) are highly predatory starfish that you must keep fed to discourage them from consuming fish living in their tanks.
Depending on the species you keep, a number of foods are appropriate for your starfish. Many pet stores that carry starfish stock preserved or frozen fish, shrimp or clams -- any of which you can chop finely and offer to carnivorous starfish. You can offer whole clams suitable as human food as well, but be sure to wash them thoroughly before offering them to your pet.
Fine-Tuning Starfish Food
Feeding an algae eater is easy -- they will find the algae living on the rocks, substrate and glass of the aquarium and help themselves. In sufficiently large aquariums, a starfish is unlikely to run out of food this way, but monitor the presence of algae in the tank. Appropriate food quantities for most carnivorous starfish are not known; some keepers are successful feeding their pet once or twice weekly, while others feed their starfish several times per week. Monitor your starfish closely and adjust the quantity you offer to produce slow, regular growth.
Because of their potential impact on mussel and clam populations, scientists have studied the feeding habits of several starfish species in the wild. While the daily food requirements vary with species, temperature and habitat, most species consumed between one and six prey items per day. A 1970 study by Howard M. Feder, published in "Ophelia," calculated that ochre sea stars (Pisaster ochraceus) consume up to 80 mussels per year.