When I had my smaller tank my whites tree frogs would constantly climb to the very top and try to figure out how to get out of the top, they would also try to attach themselves to the mesh on the lid. This stressed them to no end. You could just see them all night long staring at it trying to figure it out. If your frogs are trying to wedge themselves between the tank and the lid then it's time to get a taller tank.

In the beginning I used the repti-carpet. It was very hard to clean especially if it's still in the tank. If you are going to have it in the tank with decorations on top of it, it's going to be too much of a hassle to remove it every other day or so to clean it. Now on the other hand the frogs seemed to like it. When I put the coco-fiber in for the first time they did everything they could not to step in it and were a little upset when they got it on them (now they could care less). My other reason for switching from repti-carpet to coco-fiber was one of my frogs fell from the top of the tank and he didn't right himself or stop the fall and he fell splat on his back. I was worried that they would hurt themselves so I put a softer substrate in.

As far as getting a friend....I think he's not going to be lonely without one but it's always fun to watch multiple frogs!