We have just set our new tank up with sand and it hasn't clogged either of the filters so far...although it has only been a couple of weeks! To be honest, if you get decent sand it doesn't really swish up in the water and so wouldn't get into the filter anyway. We made sure our canister filter intake was cut a bit high, just to be safe. I remember reading somewhere that they recommend a gap of about 4 inches between filter inlet and the top of the sand to be safe.