Originally Posted by lbacha
The other issue with smooth rocks is they are hard to lock in place just ask anyone who uses them in their African ciclid tanks, they are a disaster waiting to happen as the fish dig
For helping to hold the smooth rocks in place I used a 2 part putty type epoxy from fuvel. It is also used for building salt reefs, and for anchoring corals to the rock. Took a bit to figure out how to work with it, but it works great for holding the rocks. I used it for the rocks in my crayfish tank, as well to make the pool for my salamander. The only suggestion is to look for one that dries black.