Derek,
I agree with leaving the heaters running. Also, the insulation is worth it. One other note about loosing heat, I would not use a spray bar, it is surely loosing heat. Just use the right amount of differs and air pumps to keep the O2 levels right.
I like your RDF, it has a little offset, but it should work well. After you have fish in the system, let us know how it does with the offset.
The new aerator is doing a much better job of moving the bio media. it looks good.
Keep us posted.
