I agree with SynDen - but I'm not even sure that overfeeding and heavy skimming would help a lot unless you get really lucky. PBs are *extremely* ich-prone, and they need 6' long tanks for swimming space or they get stressed. My powder ran the length of my 180 all day long like it was a racetrack- very active fish, not a slow mover or meanderer. I have seen 1 happy powder in a 72 bowfront (DyM has a spectacular powder blue), so it's technically possible, but it defies all of the odds and you prolly stand a better chance of winning the lottery. Scopas, kole, two spot, or maybe a yellow tang would be a much better choice. (note: just one of the above, not all of them)
Just my 2 cents. I know I sound like the tang police, but I just wanna save you money and frustration.