I have a big layer of potting mix under black tahitian sand. I have a bit of wood chips from the potting mix that are on top of the sand, but it still looks pretty natural. White sand and dirt seems a little too contrast. Otherwise, the sand on top tends to stay that way. The dirt becomes a clay-like layer that doesn't go anywhere. If I'm planting or otherwise disturbing the bottom of my tank, it's little black specks of sand that get tossed into the water, not the dirt. Took about three days after adding water for it to settle down, even with filtration running. About half a day any time I move or add plants. Really not a big deal. Also, fish poop tends to blend in better with the black sand, dirt, and wood fragments. That could be good or bad, depending on your circumstances.
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