Wow guys, thanks for all of the nice comments on my drawing!
I think I'll have four thermometers instead of two, one in each section.
@eemmais: I actually don't have any spare sponge filters, but I have like 5 spare HOBs.
Well, 3 are made for 10 gallon tanks, one is made for a 20, and one is for like a 40 or something. I really would only feel comfortable using the 2 that look like this:
But not really the one like this:
As the second type, for one would be more difficult to baffle, and two, it doesn't have a lid to help cover it in case my fishies decide to jump in.
Still, that's two filters made for 10 gal. tanks, would that be enough if I put one at each end along with a heater?