i dont know if this is common knowledge or not but if you want a solid black blue or grey etc background they are like a hard rubber-like material i forgot the name. cost like 2 dollars lol. just spreading the word
go to an arts and crafts store like michaels. they sell this stuff that is bascially like felt crossed with plastic. you can cut it and add to it. they dont make standard backgrounds for alot of the larger tanks. i just wish i remembered the name.
+1 to duanes. I used to use poster board, but tried the insulation and was really suprised how infrequently my heater clicked on. My house stays 65 degrees & it takes minimal run time to keep my tanks at 80.
You can get styrofoam isulation & Home Depot/Lowes. It comes in HUGE sheets. You will either need a truck or have them cut it in half at the store. Its around $12 for a sheet. I'm guessing they're 8'x3.5'