Scuzy, it also depends on how your aquascape is set up to deflect the flow, and your tank is still relatively new. Sand will move less once it matures more. I used to have only (2) 6201's in my 180g, and it moved sand all over the place. Now that the sand has matured a bit, I have added (2) more 6101s. Sand is taking it. So thinking about swapping out (1) 6101 with a 6201