I did this several times to raise the level of my sand bed. I bought a plastic tube that flourecent lights slide into to protect them (any hardware store) cut it to a few inches taller than my tank. I then cut the bottom off of a gallon milk jug and attached the tube to the spout of the jug with duct tape. You can then put the tube all the way to the bottom of the tank, fill the jug with rinsed sand and simply lift the tube off the bottom and the sand will flow out of the system leaving an even layer of sand where you want it. The tank never got cloudy. I only added about a quarter to half inch of sand at a time so it took awhile to build up the sand bed but it looks nice. Good luck