If you trying to create hidey holes and caves etc why dont you look at rocks with natural edges, divits etc. Ive done three scapes, admittedly with only a 46L tank, but I wish I had 125 litres to play with. Sometimes less is more as well. My current setup has used all I have learned in the past year of starting hobby. I also found by creating a cardboard template of the bottom of your tank, you can play with a design without the stress of it being in your tank. This way you can finalise it, memorise it ( or in my case take pics lol) and put your build. Check out my account to see my last two builds