The Genus Nardoa: Especially when started small, these species tend to get along with most all other invertebrate livestock. From the Indian to Central Pacific Oceans; Africa to the Philippines. Typified as having knobby tuberculations on their aboral surfaces. 

Not So Spiffy Choices, But Often Seen:

     Much less desirable, but commonly offered and attractive are the "knobbed" Sea Stars, Family Oreasteridae of the genera Protoreastor, Pentaster and Pentaceastor. They are distinguished by having dull spines, bumps or knobbles on their dorsal surfaces, with these often seen in colors that contrast with their overall body pigmentation. Sold under names like Red-Knobbed, Chocolate Chip, and other labels, these species are hardy but aggressive feeders, more than happy to mount and consume sessile  clams, oysters and all manner of corals, soft and stony.

Family Oreastridae: "Plump" stars. Have large, domed discs with short or no arms at all. Not easily kept... i.e. rarely live in captivity.

Family Ophidiasteridae:

About "Linckia" Stars: There are a great many seastars sold as Linckia/Linckia spp. that are decidedly of other genera. Some are not peaceful bacterial et al. detritus feeders as the "true" Linckias of many colors (and at least two species). Do make sure and get a positive identification to species, and research the nutritional, and system size and type needs before purchasing stars. The true Linckias are good choices where available in initially healthy condition, and placed in established, large systems (at least a hundred gallons) with plenty of live rock, detritus to feed on, and not too many competitors. Named in honor of J.H. Linck who wrote a monograph of seastars in 1733.  Tropical Atlantic and Pacific. 

"Other" Asteroids One Sees From Time To Time:

About Cool/Coldwater Seastars:

A brief mention of a despicable practice... the selling of colder (non-tropical) organisms, in this case seastars, into the aquarium interest. These animals rarely acclimate to warm water conditions, either falling apart within days or stress-starving to death in a few weeks. Avoid them unless you have a system designed (chilled) for their appropriate keeping. Two California, U.S.A. examples that need to be kept at 68-70 degrees F. or cooler: 

There are many other Sea Star choices, okay to terrible, but one especially warrants mention. Please click on the name to see and read about the notorious Crown of Thorns Starfish.   

Habitat:

Sea  and Brittle Stars, though they are slow appreciate adequate open space as well as coral and rocky arrangements where they can forage, hide, and find the conditions of current, lighting and shelter that they prefer. 

    Echinoderms are used as biological assay specimens for pollution, for measuring the quality of synthetic sea salt mixes, and for other test parameters. This gives you and idea of how sensitive they are. Some of them are the first to be mal-affected by metabolite build-up in water or by the presence of metallic contaminants. Should yours start "acting funny" (e.g. slowing down, refusing to eat), don't hesitate- check your water quality and make necessary adjustments. It may be better to move the affected specimen if your system water requires major changes.

    Predators generally leave these animals alone, but I would not put it past certain Triggers, large Angels, Puffers, large Crabs, or Lobsters to try out your Sea Stars out of boredom or hunger.

Reproduction:

Reproduction is by sexual means and by fragmentation. The latter capability foiled attempts in the Philippines and Australia to reduce populations of Crown-of-Thorns Stars by having divers hack them up with machetes. This merely produced more animals and added to the reef-destruction problem. Natural predators are much more effective control mechanisms.

Feeding:

Most of the Sea Stars offered in the hobby are fed bivalve mollusks (clams or mussels) or other meaty foods (shrimp, krill) once or twice weekly. In the wild, their diets are more cosmopolitan. To keep them well-fed, the aquarist will likely need to use a feeding stick to position the target food where the Star will find it immediately, before other tank inhabitants grab it or it is swept away. 

    For small specimens of the detritivorous species like Fromias, even Linckias, many aquarists rely on just placing their specimens in suitably "aged" systems that are not meticulously clean. I strongly suggest providing supplemental feeding.

Disease:

Sea Star diseases can be troublesome, especially for those with multiple specimens. Most notable are a fungus (Branchiomycetes sp.) and Vibrio bacterial infections that are primary sources of disease and mortality. Proper selection and providing an appropriate environment are not all a hobbyist can do to assure ongoing success. The use of a quarantine system for a few weeks is a good idea, possibly using special medications for fungal problems and furan compounds or antibiotics for bacterial difficulties. It bears repeating that such treatments should always be administered outside the main system, in a tank that includes provisions for monitoring water quality. 

    If one or all related organisms in the phylum start dissolving or otherwise dying in a captive system, one must act quickly- make that immediately- to arrest a total wipe-out. Changing 30% or more of the systems water and/or removing affected stock to treatment quarters is strongly indicated.

Summary:

Who needs science fiction when we have invertebrates like the asteroids and ophiuroids? When chosen carefully, the Sea Stars and Brittle Stars can provide great interest and visual appeal in the right aquarium setting. The Brittle Stars are extremely reclusive, although they may occasionally scuttle out during feeding sessions, and their valuable bio-maintenance services usually go unseen, but not unappreciated.

Bibliography/Further Reading:

Mancini, Alessandro. 1991. Starfishes in tropical marine aquaria. TFH 9/91.

Rohleder, P.G. Undated. Linckia and Fromia- Two starfish for the reef aquarium. Aquarium Digest International #53.

Schlais, James F. 1981. Walking on water. FAMA 8/81. 

Wilkens, Peter. 1974. Stars to brighten your aquarium. Marine Aquarist 5:3, May/June 74.

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