I guess your glass has been pretty damaged!!

For plants, yes. Basically, you have two options (well, three actually). If you plant them, you could either do a false bottom or what I prefer personally, a drainage layer.

For the drainage layer, you will need something like Hydro Balls (small clay ball), mesh, soil and substrate. Very quickly, add about 2 inches of clay balls, then cut a piece of mesh that covers the whole surface of the hydro balls you've just added, add about 3-4 inches of soil, and substrate (coconut husk or forest mix).

Now that you have your drainage layer, you can add your plants to the soil. When you will water it, the excess will go down in the drainage layer, where it will be filtrated. As to which plants to put in, chose one that will have the same requirements as what the Gray Treefrog needs for a terrarium. Philodendron is always a good choice, Pothos too. I like dracena, croton, green spider plants...

If you want to do a false bottom (which I find is a pain), here's a link: http://www.frogforum.net/care-articl...struction.html

It's for darts, but it will apply to your terrarium.

The third option is just to add your plant in a pot.... But it's much less interesting.

Eric