Great that is a very sturdy Mock Tank.
Two tips to make it easier for you.
1 Work at table height (no bending down)
2 Add a piece of material you can see through across the front, (about 15cm wide) by doing that you can now add a substrate, sand/garden soils work perfectly.
Now you can start a Topic and get help with your hardscapes.
Im waiting on my Seryia rock to be delivered at mo ( coming from germany good deal on zoo 8kg £20)
as going to put a peice of wood across the bottom of the box as Tim has in his video so I can add soil and sand and agreed to working at a table thanks Keith
One tip is to visit often LFS with lots of hardscape. Snipe the right pieces and collect over the time.. Good hardscape helps a lot
I don't really like ordering stones online. I understand it can be a long drive to some "good stores". But worth it in the end.. Sometimes I drive like 2-3 hours to snipe some nice hardscape