You can glue a piece of mesh to the side of the container. I also found styrofoam easy to grip and walk on. However, I still feel the best texture is bark. I like to collect twigs from the woods, and I bake them until they're nice and crispy and dry.
Thats a good idea CosbyArt, I too was thinking along the lines of screen mesh.
you can find " Heavy Duty " screen mesh that's usually black and rubber coated. Ive used it for months now with no issues. It ran me about $12-13 for a roll.
I loved the aggressive fish divider mesh ( clear type ), the holes on it work perfectly for freshlings/L2 nymphs. But I've never been able to find actual rolls of it. Just what comes in the divider kit from the pet store.