Good idea on the hair clipper comb.
To answer about sand...You keep it at a distance so that the sand falls back down but the lighter detrius gets sucked up. A little tricky, but you learn fast. Adjust the water flow rate for the height of the comb helps too. I made mine by melting a large comb and removing every other tooth and siliconed it to a piece of clear 1.25" pipe.
I hooked this to a power head to do gravel with.
Dr Joe
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