Members of the family Cucumariidae are small to medium-sized sea cucumbers, characterised by ten branching tentacles of which the lowest two are often smaller than the others. They are filter feeders, using their tentacles to catch micro-organisms and pass them to their mouth. They are seldom found on coral reefs but mostly live in deep water on sand and gravel substrates.
Certain genera including the sea apples in the genera Paracucumaria and Pseudocolochirus, contain toxic holothurin and holotoxin and release it into the water when damaged or killed. Spawning may also be accompanied by release of these toxins. For this reason, although they are interesting and attractive to keep in aquaria, it is inadvisable to keep them in a tank with other reef species.