Starfish are divided into three classes; Asteroidea that contains Sea & Cushion Stars, Ophiuroidea that contains Brittle, Serpent & Basket Stars, and Crinoidea that contains Feather Stars & Sea Lilies in the Subclass Articulata.

Even though some starfish species do eat algae and most are scavengers that come out at night to feed on detritus and debris, here are some other important things about them that need to be considered before buying one.

Depending on the species, many ARE predatory animals that will often attack and eat a wide range of invertebrates such as other starfishes, urchins, sponges, anemones, soft and stony corals of all types, coraline algae, clams and other mollusks, crustaceans, and sometimes even unwary or sleeping fish. Some starfish will survive in an aquarium if fed bits of clam, shrimp or other meaty fares, even though this might not be their natural diet.

• Sea urchins are used as indicator organisms in public aquariums to determine if the system is functioning properly? Because these animals are so “picky” about water quality and cleanliness in an aquarium, they are the first to show signs of stress, seen when their spines are laying down or falling off.
• There are numerous varieties found in both tropical and colder water oceans around the world?
• Urchins are generally referred to as Wana (sounds like vawna) in Hawai’i?
• It is not unusual for some urchins to house tiny, species associated shrimps within their spines?
• Triggerfishes and Puffers will pick the spines off sea urchins, turn them over, then break open their shells to eat them?
• Prior to the early 1970’s, sea urchins in California were considered nothing more than pests, but now the export value of California’s sea urchin fishery is a multi-million dollar industry?
• Many species enjoy eating coralline algae? This is not necessarily bad, unless you place too many in number and/or of large size in a tank where their appetite can exceed the amount of coraline growth available for them to feed on.