Walking Dendro

About

The walking dendro (Heteropsammia cochlea) is one of the most biologically unusual corals you can keep, and its common name is not an exaggeration. Unlike virtually every other coral in the hobby, this species is completely free-living. It does not attach to rock or substrate. Instead, it houses a commensal sipunculan worm inside its base, and that worm literally moves the coral around on soft sediment, keeping it upright and preventing it from being buried. The relationship is obligatory: the coral and worm depend on each other. Many specimens also carry a small embedded mussel as an additional passenger, making this essentially a coral that functions as a tiny ecosystem. In the wild, it comes from the Indo-West Pacific, typically found at depth on sandy or silty bottoms rather than on hard reef structure. Coloration tends toward muted tones, pale grey, orange-brown, or a dull green, so this isn't a coral you'd keep for bold color. What you keep it for is the behavior. In the aquarium, a sand bed is essential so the worm can do its job. Flow should be moderate and lighting relatively low, consistent with its deeper-water origins. It is a genuine conversation piece that rewards patient, observant keepers.