This is not something I have not done but rather something down the road I am planning to attempt and not sure if it would work (fair warning) but I think other have done this to make moss walls (not sure). Using that plastic mesh you get from the craft store for knitting (the kind used in algae scrubbers) rough it up dragging a hole saw over it to provide a surface that's easier for the moss to attach. Pick your moss of choice (I like Christmas moss but I'm bias in my opinion). Then drag the moss over it and it will catch on sharp edges (alternatively superglue the moss but you still want to have a rough surface for it to attach as it grows. Attach to the aquarium where you see fit. A small rock(s) superglued to the back or zip ties as I see in you photo's (lots of different methods). Not sure if this is your cup of tea but thought I would share.
Dan
Dan