[BigV]

The same solution for both scenarios is insulation. I would look into a sheet of the rigid building insuation. It comes in blue and pink, you know, like very fine grained styrofoam. Cut panels the size of the sides of the tank, including the bottom and, more importantly, the top. You can leave holes for throughways for air, lines, cords, etc, but fewer and smaller is better. The bottom one could live under the tank permanently. Depending on the viewing angle, the one on the back and maybe the sides could be permanent or semi-permanent too. Then when the cold rolls in and there's danger that the room the tank is in will become too cold for the heater to keep up, you could put more panels on. Imagine a styrofoam cooler you take on a picnic. It keeps ice cold for a long time with a *big* temp difference 30 deg versus 100 outside. You need to keep the tank at what, about 70 deg F? Then this setup could give you protection when the room is as low as freezing. That would be a lot of protection.

Your heater can't heat the room very efficiently, but the tank is a much smaller thermal mass, and conserving that heat in the tank, instead of radiating it into the room means the heater can keep up. Probably. I'm just blue-skying here.