I may have missed this but what size is your UV? With the plumbing scheme you have, you will have to match the flow to the UV as you suggested. Have you considered putting the two canisters on separate loops? You are pulling water for three pumps in the existing diagram - this will need a pretty big pipe to handle the flow and prevent cavitation. What diameter pipe are you going to use? If you just had the two canisters they would share an intake but one could return to your spray bar and the other to the top of the tank. If you plumbed the UV into one of those lines I would gues the flow would be appropriate for killing algae & bugs. For flow, you could add a power head internal to the tank and save some $$ on electricity. When your plants grow in they can hide the power head pretty well. I am sensitive to the electric cost as Califonia has a sliding rate scale ( $0.28/kWhr). With three pumps at 140 watts each, our bill jumped 60% over last year!
I would also suggest moving the ferts to a post pump position so you don't feed the filter sludge before the plants. You will have happy bacteria but could cause slime to build up quickly in your filter.
Looks like fun though, I think I need to another project!
Bill, you got me thinking about energy cost in general, so I did a little work up:
That's my estimated energy cost for my 120g. I didn't include my DIY controller, pH controller, and co2 solenoid because they are comparatively insignificant energy consumers.
The MD 7 will cost me about $35/year to operate. If I downgraded to a MD 5, it would only save me $13/year, so that ultimately doesn't seem worth it to me.
However, it gave me the idea of setting up the MD7 so that it was only on when the co2 solenoid is open. Best estimate is total 3 hours a day in that situation, bringing operating cost of the MD7 down to just $4/year.
The downside I foresee is wearing out the pump by the many cycles on and off per day. A lot to consider.
Edit: After analysing a little more, what might be the most intersting thing is that the MD 7 would be the largest power consumer, if left on all day.