This is a very simple thing which I will be using for several rocks in my 90 Gallon tank. Due to having larger fish, rocks are prone to get knocked around and fall over. Never a good thing in any aquarium. This thread will show it though on rocks outside of the tank. The epoxy I used is good inside the tank, as well as out of water.
I will be using this to hold big and heavy rocks to each other in the tank, but this was a special application. I had several pieces of tonga branching rock in my tank, none were huge, but nevertheless they sell for up to 10 dollars a pound. I picked out the tonga pieces and decided I wanted to make a branching formation for the side of my tank.
1. Gather the epoxy, and the Live rock
2. Figure out the way you want them to hold together
3. Knead the epoxy to mix it thoroughly
4. Make sure to attach it firmly in the connection areas
5. Let is set and cure for 12+ hours