If you want to mimic field conditions, you will need a mix of sand, gravel and coral rubble and shell with pieces ranging in size from pea to golfball. One or two large pieces of LR on top of this will focus the animal's digging. If the consistancy of the substrate is right, it should be able to build a burrow. However, this doesn't always work, so it is probably easier to use a length of grey or black PVC about 2 inches in diameter. Sometimes if you bury the tube with rubble, the animal wiill exten the burrow and it will look natural. A tricky part with this is whether you want to go the plenum route or rely on the life rock and skimming, etc. I usually don't construct a plenum, but rather pile up the sand, gravel and rubble on one end of the tank leaving most of the bottom with only a thin covering..
Roy
