During the hours after the aquarium lights shut off, many of the invertebrates in the aquarium become more active. These include the snails, crabs, shrimp, and especially starfish. As these invertebrates search the rocks for food, they will often rearrange the rockwork in their quest.
One solution to this problem is to use an underwater epoxy to glue the rocks together. This is accomplished by simply breaking a small piece of epoxy off of the stick and kneading it with your fingers until mixed. The epoxy is then ready and can be used to bond the rocks together. It's important, at this time, to turn the protein skimmer off for about 24 hours until the epoxy cures. The chemical reaction that takes place within the epoxy is safe to invertebrates, but produces a by-product that effects the protein skimmer's efficiency, causing it to produce very wet foam. It's a good practice not to epoxy down the corals until they have been acclimated and have fully expanded, giving you a better estimation of how much space and light is needed for each individual.