Reef Rocks are perfect for the propagation or fragging of soft corals such as zoanthids, mushrooms, star polyps, Kenya Trees, Xenia, ect. They are designed to be more attractive than disk or plugs by having varying shape and height giving a more natural look with the corals being propagated on them. And yet still having a secure flat bottom so they do not roll around or move easily like using common rubble rock.   They are bright white in color, measure about 2" in size and a .5" thick.  They are made from a fused special grade bright white reef sand.  This sand is a natural calcium based sand which has been shown to speed the spread of coralline algae growth and corals on the rocks.