I wouldn't use the wire kind. Worst case scenario, it rusts leaving possibly harmful deposits in your water. I'd use fishing line/cotton thread for the moss rock too, although I wouldn't be able to tell you for sure if it will attach to the rock if it's not porous. I do know that christmas moss sticks to anything, including glass, so if you don't have any luck with vesicularia dubyana (java), you can use vesicularia montagnei (christmas). When useing lava rock, any type of moss will attach to that.
You could use plastic canvas, which is used in a form of crossstitching, for your wall. Use suction cups to hang it on the back of the tank. It comes in different sizes, but I'm not sure how big or small. Look in craft sections or craft stores. This is also a great divider.
