Backyard Aquaponics
A place to discuss aquaponics

Here's a cheap Solar Heater we made that works really well, and you can put together in a weekend. It runs a small fan for circulation, not totally necessary, but greatly improves performance:
http://www.instructables.com/id/Cheap-a ... ar-Heater/

And here's the Spanish version, if you need it:
http://www.instructables.com/id/Calenton-Solar/

Ive been thinking of building something like this for the shed with my AP system. One question about the fan, could you not use a smaler 12V solar panel directly wired to the fan, so if the sun is shining the fan spins, then stops when there is not sun?

Yes, you can solar with this, this fan I'm using is 12 VDC. You'd probably want a small battery, as well, just to help with the start surge and could get away with a smaller panel. I think the fan I uses needs about 10 watts or so, better to get a slightly larger panel, maybe 15-20 watts.

You don't want the solar panels turning the fan on and off, you want the temperature (snap switch) to do that. It's a $5 part and easy to install in line, so when the panel is hot, it blows air into the house.