Invertebrates Echinoderms

Echinoderms are the hardest to find in the aquarium trade, although they are fairly resistant and survive well in a tank.

Sea Urchins
Sea Urchins are not very easy species to acclimatize. It is possible to keep one small specimen at most, which will often live away from the light. They are herbivores that sift the substrate looking for algae to eat. In among the prickles it is possible to see the articulated pedicellariae, which end either in a tiny pincer for trapping food or a sucker. The latter allows sea urchins to develop on rigid supports or the glass sides of the tank.


Some species of sea urchins with varying sizes of prickles can be found in saltwater aquariums.

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Eucidaris tribuloides, native to the Caribbean.

These crawl over the decor to graze on the algae which form their diet. Be careful, because they are highly prized by Balistids, puffers, and some Labrids, which have teeth strong enough to break the internal calcareous skeleton of sea urchins, and do not seem to be put off by their stings. The names of the extremely few species available are not known with any precision. Size: 10 cm.

Starfish
Starfish are not recommended for a saltwater aquarium, as they attack other species, such as sponges. Starfish are in fact either carnivorous, gripping their prey with their long arms that emerge from a central disc, or microphages, in which case they feed on small organisms on the bed.

The ophiuroids, sometimes called brittle-stars and closely related to starfish, have articulated arms which allow them to move around quite quickly. These arms, like those of the starfish, can regenerate themselves if they break off.

These survive well in an aquarium. Worthy of note among the carnivores are the Protoreaster and Oreaster genera, which feed on other invertebrates, especially the bivalve mollusks. They must not be kept in a tank with other invertebrates. Feed them with raw or cooked mussels. Other genera, such as the Echinaster, Linckia, and Fromia, are microphages and feed on the assorted debris found on the aquarium bed. They are preferable to the carnivorous starfish in an aquarium. The ophiuroids are attractive echinoderms in a saltwater aquarium; they can be accidentally introduced with live rocks. Size: 10-15 cm.

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Linckia laevigata, a microphage starfish that can cohabit with other invertebrates.