I bought a 6'x8' section of fence at Lowes and cut it in quarters. I put 3/4" Styrofoam insulation next to the tank, then finished out the walls with the fence. Our temps were in the High 90's to low 100's and the tank water was an even 84 in the day time (peek Heat), and 75 at night. the other tank has the wall with dirt. It worked the same.