As with many aspects of saltwater aquarium-keeping, aquarists tend to be very opinionated about whether or not it is a good idea to keep a sea cucumber in a marine tank. In reality, it is not that complex of an issue, but it is one that requires the aquarists to make some key decisions about the type of tank they plan to keep and their commitment level to maintaining an environment conducive to the health of a sea cucumber. This article attempts to give the aquarist the information they need to make such a decision.

Sea cucumbers are echinoderms (phylum Echinodermata)—related to starfish, sea urchins and brittle stars. Taxonomically-speaking sea cucumbers are part of the subphyla Eleutherozoa or the motile echinoderms (as opposed to the sessile echinoderms like crinoids). The phylum name translates as something like “spiny skin,” but the sea cucumbers so-called spines are really like bumps or warts. Sea cucumbers mostly feed by 1) collecting food with feeder tentacles or 2) “vacuuming” sediment. It is the latter type of sea cucumber the aquarist will probably want to add to his or her system given their capacity to clean and constantly shift the upper layer of the substrate.