You can attach moss in several different ways. My personal favorite when dealing with a foam or cork background is to use Floral wire. Cut a small 1in piece and bent it into a U and then press it into the moss. You can also use glue (hot glue, super clue, epoxy... Just a small dab and press the moss into it), silicone, zip ties, Lay the tank on its back and let the moss grown laying on the wall for 2 - 4 weeks and see if it attaches itself.
So many options![]()