If your insistant on keeping the intake close to the bottom here's another idea I thought of last night. Ttake a piece of pvc pipe with a cap on on end and slide it over you intake. The pipe should be about an inch wider than your intake. This will then act like an overflow with the open end facinf upward and the capped and downward. The water will flow down into the pipe and then be taken up by your intake. This should keep most of the sand out of your filter. You could even drill holes in the pipe higher up towards the top to make sure that if the water level does drop below the lip of the pvc pipe you pump will still have water and not burn up. Just a thought and haven't actually tried it myself but if you do let me know how it works. How you fasten the pipe to the inside of your tank is up to you but personally id just take some sution cups u can buy at most pet stores and stick them to the back of the pipe