Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
As for 'scaping materials:
You could use real rock, but that is going to get heavy, and not stack up so high. OK in the tank, but I would not go much higher than the rim of the tank because of the weight.
A lot of these use wood of some sort, then attach stuff to it. You can use a thick sheet of acrylic as back and side walls. No matter what you use, I would plan some kind of nuts and bolts to attach things.
Cork bark is very common.
Styrofoam covered with something for texture and color:
Expanding foam filler can work.
Concrete that is a lighter blend (not pure sand and gravel). It can be tinted different colors as you build. Mortar, thin set and related materials may be better- the aggregate is finer, no gravel, so the finish can be applied thinner, and in layers. Sika product line includes some food grade products that you might look into.