the foam is great stuff. the home construction expanding foam. it is waterproof/animal safe. the submersed section will be covered in brown silicone and a mix of pebbles, coconut fiber and peat moss. (just to make sure it stays a black water tank
) the land section will be covered using titebond III wood glue and coconut fiber. the exception to the land will be the water feature(s) will be covered using silicone. the titebond is waterproof when it cures, but i want to avoid any problems with "erosion". water is a pretty destructive force when it gets it's groove on, and i know silicone can hold up to constantly moving water.