The fish are behind this [not sure if that is a pun or not...but not meant to be!]. I have play sand in my tanks, and I never see anything on it but when I do the water change each week I can certainly stir stuff up, but it is more a cloud the particles are so small. I have smallish fish. If I had large fish I am sure I would see it. Even in my cory tank with 40 average-sized cories their continual sifting through the upper sand never stirs up particles larger than what could only be described as a slight cloudiness.
Snails help with this, because they eat all the organics (fish excrement especially) which breaks it down faster so the bacteria can handle it quicker. I have dozens if not hundreds of pond snails in my tannks, and undooubtedly that makes a difference too.