If my tank is in a cold part of the house, would attaching a sheet of 1/2” rigid foam to the back help reduce heat loss? Wondering if anyone else had thoughts on this.
It will probably help, but IMHO, only a tiny bit. I think most of the heat loss in a tank is the water surface, especially if there is air movement over the water. If you don't have water oxygenation issues (or CO2 issues) you might consider a glass top or even an insulated top cover.