I don't know if this helps, but in the past I have used a smaller tank at the same level as the main tank as a refugium. I used U-tubes to keep the water of the two tanks at the same level, and used a powerhead to return the water to the main tank.(Maxijet 400). In my case there were no heat problems. The main tank was a 33 Gallon semi cube and the refugium was a standard 10 gallon tank.
