I cut sections of black, large diameter ABS pipe to support several large pieces of my rock. Drilled holes into the sides of the pipe as well to allow for some movement of sand & prevent stagnant areas inside. Will probably do the same for my next build, but this time I'll plan a little better and silicone the pieces of ABS to the bottom. Gets the rockwork higher & mostly out of the substrate so you get max benefit from your LR. Certain types of ABS tend to float & since my system was purchased second hand, I was aquascaping with water & critters in the tank, positioning the ABS pieces was a chore with them wanting to float away on me. What I found good about the ABS is that different lengths can be cut to raise certain rock features a little higher. You can also serrate the rim (cut the edge of the pipe) to make notches for the rock to fit into. Can be a bit fiddly I guess, but if you're in the planning stages with a dry tank, should be easy.
My Maroon clown tends to rearrange the sand around her territory and she's exposed a section of the pipe, but it's partially covered with coralline now, so not too much of an eyesore. Here's a quick pic of a section of ABS halved. All the pieces I have at the moment are full circles with holes cut in, but for next build I might try this & silicone them down once I have the rock work the way I want it. Need to clean up the cuts of course.
