Bryan, is there any way to get a bigger sump? Increasing your total water volume will help a lot.
For your rock, I would recommend a lot of water changes and frequent scrubbing and rinsing. I usually try to do the scrub and "dunk rinsing" several times a week, and then change the water out. Its a big hassle, but agitating it and dunking/rising will get all the crap out of there - it's the best shot at reducing the phosphates and "hair algae food" that is trapped in the rock.
Thanks for the input! The main reason I was using that sump is that it came with the tank and like the size under the tank but I could probably do a wider sump. What size would you recommend?