Jabo,
Nice pic!
I have three power heads with foam prefilters that I have going in different directions in a 65 gallon tank. The foam catches alot of excess food and detritus which flows into it through uptake into the powerhead. So I rinse these out every few days. Plus once a week I like to take my turkey baster and squirt water on the rocks from close range to dust them off. Do you have enough current to avoid "dead space" where dust can accumulate? Also do you keep a cleaner crew going over the rock, like blue legged hermit crabs, etc.?
c-c