Yeah the extruded pink/blue foam and Drylok (original) latex is the best IMO/IME. I have been looking at other methods but they use the expanded foam and 2 part epoxy or resins and lots of sand for texture which is HUGE mess for both cutting and covering. Yeah the hot knife stinks, but I won't have a bazillion white bubbles or light foam flying around the neighborhood using saws to cut the extruded foam. Even if I texture with wood files the pink stuff is denser.
I have been looking at videos of divers at Lake Tanganyika to get an idea of what the rocks look like. There are NO holey rocks or seiryu stones in sight!

Thought is to make 3D boulders that are flat on one side so they can be attached to the back and bottom of the tank. The boulders will be scaped to encourage gaps and cracks both within the "rocks" and when assembling the rocks.
Also we will be having a section for shellies so it will kind of be an attempt to do a rock "wall/cluster" starting about 1/3 from the right side and wrapping along the back to the left side of the tank. This will also solve the issue of the tank being in a higher traffic area and spooking the julies. I am going to paint the tank a beautiful jade blue to replicate the colors of the water at a certain location/depth.