The 600 plus species of Crinoids (feather stars and sea lilies), and the 2,000 species of Ophioroids (serpent, brittle and basket stars), are lumped into this one article not because of their closeness of kin, but because they share many features, and both are uncommon in aquariums. Both groups lack or have reduced tube feet and anus, and on a superficial level share many ecological and morphological features. As with all echinoderms a slow careful acclimation is necessary to avoid osmotic (salinity) shock. Now let look at each group more detail. 

The Crinoids are the most primitive of the Echinoderms with a history stretching back over 400 million years. Some primitive groups live attached permanently to the substrate others can actually swim by beating their feathery arms. Lamprometra is a common genera. This animal lives in the Caribbean. Anchored by structures called cirri, it uses its upturned arms to filter the water for microscopic plankton. They are harmless to other animals and much care should be taken to see that no large invertebrates (crabs and shrimps) or predatory fish pick on them. They like a tank with dark crevices that have a strong water flow. A liquid invert food and live plankton feed right at dusk will stimulate feeding. Briefly (1-2 hours) turn off external mechanical filters to insure that they get some food. They are quite delicate, and should only be placed in well established invertebrate aquariums that receive regular feedings. 

There are three principle types of Ophioroid body plans but before we discuss their specific biology, lets review some points pertinent to all ophioroids. They are for the most part small harmless bottom dwellers, that either filter feed or scavenge. 

Serpent Stars are surprisingly mobile and many species will rapidly hide from the light if exposed (a phenomena call negative photo-taxis). The first two groups are the serpent and brittle stars. They can be distinguished from one another by the many small protuberances that are on the surface of brittle stars. Both have an interesting habit of casting off an arm if provoked, and will quickly generate a new one. 

Brittle stars (i.e. Ophiothrix) are small harmless filter feeders, that are a common component of well established live rocks. Serpent stars (i.e. Ophioderma) are larger somewhat more active predators that might even catch and eat a small slow moving shrimp or fish. Both enjoy a well established aquarium with plenty of places to hide. The smaller specimens do well on a diet of liquid food, and the larger enjoy a small chunk of fish or squid every 1-2 weeks. 

The final group of ophioroids are the bizarre basket stars (i.e. Astrophyton). They resemble a circular mesh of tentacles and share similar demands to the Crinoids when it comes to a tank. There is nothing quite as bizarre as watching one of the softball sized lumps unfurl into a two yard wide mesh of arms as the sun is setting on the reef. The smaller ones occasionally available through stores are equally spectacular. These two classes of echinoderms while quite secretive and rare, are well worth a second look.