Backyard Aquaponics
A place to discuss aquaponics

Thats the best idea, compensate for limited hours of winter sun by using external collectors which increase the capture area.
Keep the differential low to reduce losses and use air as it responds much faster than water. The idea is to grab the heat as it appears and move it as fast as you can into the insulated mass.
I have about 1500 of the 2400 aluminium cans i need to build a supplemental fence mounted collector, in theory could produce upto 15kw/hr using winter sun.
It should work with a -6C winter low which seems tropical compared to -25F.

Turns out I probably won't be using the HFGH for this, but building a custom GH. This has been done here in zone 4, with extra heating adding up to $75 for the entire winter:

Northlands Winter Greenhouse Manual
Garden Goddess Enterprises