Red-knobbed starfish (Protoreaster linckii) are also sometimes known as African red knob sea stars or red spine stars. Despite being generally peaceful, they are carnivorous and will eat almost anything small enough to consume. Although they can get quite large, members of this species can be kept in a home aquarium by an experienced marine tank keeper.
What They Look Like
As their name suggests, red-knobbed starfish are red in color, with spiny protrusions -- known as tubercles -- coming off the top side of their arms. Some white markings link up their tubercles, giving them an almost grid-like appearance. Fairly large, these sea stars can reach up to 12 inches in diameter. They have five arms and a red underside with pink podia -- or feet -- and a central mouth.
Where They Live
Red-knobbed starfish are marine creatures, which means they can only be found in the ocean. This species lives in the Indian Ocean, usually around Indonesia, the Maldives and Africa. They like to live on sandy or muddy sea beds, where they can most easily hunt their prey and forage for food. Although often seen in shallow tidal pools, they can reside at a range of depths, right down to 100-foot-deep reefs.
What They Eat
Carnivorous creatures, red-knobbed starfish eat a whole host of different sea critters. They're opportunistic hunters and will munch their way through all sorts of corals, sponges, invertebrates, worms and even other sea stars. They don't eat in a particularly traditional manner -- they have no teeth to chew their dinner so they push their stomachs out through their mouths and engulf their prey. Once they've started to digest, they can pull their stomachs -- and their meal -- back inside to finish eating.
In the Home Aquarium
Despite their large size, red-knobbed starfish are relatively hardy sea stars that can be kept at home. Although they're not the most difficult starfish to keep, they still need a lot of care and aren't suitable for beginner aquarium keepers. They need to be kept in a large -- minimum 75-gallon -- fish-only marine aquarium. They're not reef compatible, as they'll end up devouring most of the other inhabitants. Water temperature should be kept between 72 and 78 degrees Fahrenheit and pH between 8.1 and 8.4.