Blue Linkia Starfish (Linckia laevigata)

That saturated blue coloring makes Linckia laevigata one of the most photographed sea stars in the hobby, but it's also one of the hardest to keep alive long term — this species is a specialist biofilm grazer with a genuinely poor track record in captivity unless the tank is large, mature, and loaded with the microfauna it needs to survive. On the upside, it can regenerate an entire new body from a single arm with a fragment of the central disc still attached, a process that produces a temporary, lopsided form aquarists call a "comet."

Care level: Difficult · Temperament: Peaceful · Max size: ~12" arm span · Min tank: 100+ gal, mature · Reef safe: Yes · Diet: Detritivore, grazes biofilm