Though, the moss might get sucked into the filter tube if you don't put a sponge over the intake. Good luck.

That shuld be fine, as long as there is nothing flush with the back wall.

Excuse me. I found your post on a moss wall and do you mean helping me with something? You mentioned that nothing can be on the back wall of the aquarium otherwise it wont work. I have a filter tube that comes from the filter and is 1 1/2 inch awaay from the back away from the wall. Is this ok? Thanks alot