Well from now, eventually the small dust/sand particles would sink to the bottom layer of the sand, while the ones around the top will be kicked up by your fish. Every weekly waterchange I do, I use my hand to violently stir and churn the sand, so trapped gases can escape and some fine light debris can be sucked up by the filter. Another thing, becareful with churning sand around your filter, make sure a big lump of sand doesnt get in, I've read it can hurt a filter impeller, thought I've never seen that happen. Just something to be aware of that's all. -Jeff