I insulate the tank with a product called Reflectix - it's like bubble wrap covered in foil. It's works great! I put it on the back and sides of my tank, as well as the walls behind it. Since we don't believe in stable temperatures in my house, it's helped a lot to control my ambient temperatures. I also cut a sheet of 1/8" Plexiglas and stuck it to the front of the tank using blue tack.