I've used it.
Get one of those plastic tubs used for mixing paint at the hardware store. Read the directions closely and mix the clay with water.
You can then put it in the tank and use your hands or a paddle or something to form hills and get it the way you want. It's going to be quite damp and will raise the humidity in the tank until it dries out so keep that in mind. It dries solid and hard, but the surface can be scratched at by the Uro's to slowly remove clay and they can form tunnels and burrows.
It will stain everything. Even the uro's. So, if you're using a glass tank this won't be a problem. Just be prepared that if you don't like the substrate, change your mind about it, you'll have to remove the dried out Excavator and clean the remains and this is messy and time consuming.
My Peter loved it and spent quite a bit of time making a burrow. I helped him a little and used a spoon to start forming a hole on the side of it and he took over from there.
He then spent everyday inside his little hole, never came out to bask or eat, just occasionally poked his head out. His tunnel was deep enough to where I had to use a flashlight to see if he was still in there. I was worried that I wasn't able to see him, and got worried that the cave would collapse on him or something. Thats why I ended up removing the substrate. Peter is all white on the bottom and has yellow/black markings, and he was stained that brick red color until his next shed. His feet were CAKED with clay from digging, and he walked around with little clay shoes. That just didnt seem right to me, so I ended up getting rid of the Excavator.
