New Enclosure for Map Turtle

[jocie1976]

I am just starting a build for my cousin's Mississippi Map Turtle. The pictures show what she wants me to build. The filter will be under the land portion, the land portion will be siliconed in place on the glass sides. The land portion will have some Hens and Chicks planted around the glass sides and be open with either sand or moss in the middle (to be decided yet). The wood piece will be siliconed to the edge where the turtle would climb onto the land, and the wood edge will be under water. The tree underneath is to support the land mass and will be siliconed to the bottom of the land and to the bottom of the tank. She plans to use the rocks in the somewhere, but not necessarily in that position. She plans to have a heat lamp over the land area for basking, enclosed with a screen lid. The water area will be heavily planted.

Can anyone see any problems with this design? It is a 20g tank (an upgrade for the turtle), the turtle is a couple of years old (about a 4-5" shell), loves to swim, loves to bask, eats well.

My main question is: What can I use to disguise the sides and bottom of the land portion. It is a Tupperware container, cut to fit. The sides are rough and I can roughen them up more if needed. Most of the underside will be sitting in water so however I treat it needs to be water safe once cured. She would like it to look as natural as possible. Any ideas?