Interesting theory. By observation though, I think he gets about the same since I feed the DT tons of algae. Percentage-wise, the powder blue only makes up probable estimated 1/20th the volume of fish mass in the tank, since he's one of the smaller fish. I think in your tank, he was the biggest, along with the foxface and a wrasse, if I'm remembering right.
I'll give the UV being plumbed directly in the DT some more time but if after the January meeting, things haven't cleared up like they usually do, then I'll look into full fish removal for 10 weeks to rid the system of ich.