After taking some time and looking at bunch of pics, came up with few new things. Got annoyed last night, as I was wasting time just standing around and looking at rocks, so took masonry bit, drill, fiberglass rods and went at it. Came up with 2 structures
Right side:
https://youtu.be/p4glY8MmGkw
Left side:
https://youtu.be/LPtnkZrwaOY
Right side max height is 12", so 1/2 the tank height. Left side is around 14-15" at the highest point. I started adding random small pieces (being held by rubber bands) as they are too small to drill, and want to see what it would look like. Hope that by adding these to the left side, it looks more like rocks, and not just boulders stacked on top of one another. Feedback, critique, and so on always welcomed and appreciated. Thanks