Just a point of clarification here. You have a 30g tank and you're running a 10x12 single sided screen. Going by the feeding-based method, that screen can handle 5 cubes per day. I would suggest
1) trim the bottom off the screen, leaving only about 1" max to 'dip' into the water (the rest does nothing for you)
2) reduce the width of the screen such that you have 24 square inches (L x W) of illuminated area for each cube you feed per day. This would probably mean you can reduce to 4 wide x 6 high. This will also dramatically increase your flow per inch and you may have to widen your slot a little if the overflow starts backing up.
3) Consider eliminating the shutoff valve, or just shut it completely. This valve being open is in effect lowering the pressure to the slot and allowing algae to grow into it and block flow more easily as the water has a secondary pressure relief path with zero resistance (bad for flow to screen)
4) Your reflector design is great, the aluminum foil may not be the best thing to use. If you can get a smooth material, like the one SM has
http://www.santa-monica.cc/Flexible-Reflector_p_15.html that might deliver a little more light to the screen. The aluminum foil has a scattering effect. This is not so critical, just sayin'.
5) consider putting in a larger wattage CFL and cutting the hours down. Check out post #17 here
http://algaescrubber.net/forums/show...cs-The-Summary
Still, with all that, You dropped N from >100 to less than 20 in a month. This shows how powerful these systems can be! You'll have this system down and clicking along in no time.