Burrowing Sea Cucumbers, or sand sifting sea cucumbers, are most likely either Ocnus surinamensis or Phyllophorus occidentalis. Both are very popular for sand and mud sifters for reef tanks and refugiums. They spend all of their time under the sand burrowing through it, and about the only thing you’ll usually see are the dendritic feeding tentacles, which line their mouth. These tentacles dont seem to be able to sting but they somehow catch and trap sediment and detritus, which they ingest and eat, then periodically expel and start catching more stuff. They are one of the only cucumbers that actually live under the surface of the sand, and they do burrow through it, but not very fast and not very far.
Since they live under the sand, they aren’t much trouble to any other tank mates. As far as I’ve been told, they are reef safe and coral safe, and
nothing seems to eat them. Most customers buy them as sand sifters, and they are good at that.
Like some other sea cucumbers, they can release a toxin when stressed, but it takes a lot to stress them, and unless you have dozens in a smaller tank,
there arent enough toxins to cause a problem. When you acclimate them to their new tank, it would be a good idea to discard the acclimation water after youve introduced them to your
system so that any potential toxins released during shipping are not introduced into your system.
These are small cucumbers. They will get up to about 3 long when full grown, but can also shrink from 3 to 1.5 if disturbed. They will be about the size
of a pecan when you get them.