Placing a Tank on an Uneven Floor

[Frogger]

You can't really shim a wood floor, the floor will dent where the shims are. I made a small wood frame and poured self leveling concrete over my wood floor. I placed a thin layer of plastic under the concrete so it wouldn't damage the floor. I removed the wood frame, painted it black and my tank is now perfectly level. The concrete is between 1/4" and 3/4" thick.