I have 1 - 1.5 inches of sand in my AP12 and I don't have any algae on the surface. I'm not sure which critters are keeping it clean but I suspect the 12 small hermits are shifting it enough. The only algae the tank has ever had is the 2 day old brown haze on the glass which the magfloat cleans in a jiffy. Oh and LOTS of coraline!
I slope my sand high in the back, shallow to front so the sand at the front is level with the black trim.
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