I just use a 3/8" tube to siphon out my water. The flow is low enough to control sand being sucked out but strong enough to get the loose gunk when it's an inch away. I do what Luna says, I pinch the tube if I see that sand was sucked up. Sand sifting stars can also clean it up.
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150G Custom All-Glass 48"x24"x33", Bubble King Mini 180, CR-2000 Wet/Dry sump, 380W MH/CF Hamilton, currently with LR and my mean 3-strip damsel, lionfish and porcupine puffer
20G Top-Fin, CPR Bak-Pak2, 70W HOT HQI Hamilton, T5 2x24 actinic supplement, Aquacontroller Jr., 2 maroons, BTA nem
65G Clear-For-Life All-in-one aquarium, Aqua-C EV-180, 130W Coralife CF Retrofit, empty
12G JBJ Nanocube 2 misbar ocellaris clowns, AquaticLife 115 skimmer, upgraded to 2 Current USA LED lights. | 
