This is what we are doing this year...
We started with two 30 inch strips of 11X12 flexwatt side by side wired together and plugged into a Herpstat.
To control the fan speed we used a zoo-med rheostat, we took apart the case and took off the female plug-in part so we could run the wire out of the inc since we wanted the rheostat dial on the outside of the inc.
The fan we picked up at home depot has a male plug-in making it as easy as that, plug it in and it's going.
Then we put wood running up each side of the back and screwed a piece of plastic(shower stall plastic) cut to size so it fits from the floor up to almost the top of the inc.
Then we took the fan and traced around the outflow tube and cut a hole so the fan would blow air from the inc into the area behind the false wall and up and over the heat tape, then escaping out the top of the inc to be recirculated back to the bottom and into the fan again.
We went to all of that trouble because we noted that all of the tubs on the ends closest to the heat tape were a degree or more warmer than the center of the tubs.
Will it work with just heat tape on the sides and the fan blowing towards the back of the inc?
It certainly will, we had it that way that last couple of years and had a 100% hatch rate, we just didn't care for the small temp difference so we solved that issue with the false back(something I saw first on this forums by someone else)
For water we use the one gallon bottles and put as many as we could fit into the inc up top and on the bottom, effectively giving us 3 shelves to put eighteen 7 qt tubs on.
We had 16 bottles of water, 8 on the bottom around the fan and 8 up top.
Hope that helps...