OK, here's a more pressing conundrum;
This shot shows the light transmission through a FOUR day old screen with new, reflected cfl's (this side has just been cleaned);
and in the interests of comparison, a reverse shot through the same screen using the LED UFO;
so, after 4 days, there are parts of the screen that are not being bathed in light (and this is 4 days on one side only). The conundrum is "why do these sections continue to grow" for another 5 days in my case.
while I'm here I may as well post the picture of what algae created organics actually looks like when aerated (not rinsed my screen after harvest for last two cleanings). The skimmer goes crazy for a while, then these extra large bubbles subside;