fwiw, I've been playing with an apex flow meter and UV to track any kind of changes that are typically reported. Its a 56w aqua ultraviolet. I've ran flow at 1000-1200gph, 800-1000gph, and 500-600gph.
I've noticed no difference to anything really. As if I never put it on. I did push up some feeding slightly and spurred some cyano/dino growth. Nothing major just wanted to see if I could at each level if flow and so far the UV has had no impact on the ability to cause the minor outbreak or speed up the removal of it. Both major types of dinos are alive and well in my system but still controllable through my normal routines.
I'm currently spurring it on and testing 400-500gph flow through the UV.
I took this picture a couple nights ago. Bottom left you can see a small amount of cyano. Like I said just pushing it enough to spur on a tiny amount.