hey leslie.... there is actually a pretty easy way to do this... i forget how its done but it something to do with a pipe i no someone on here has done this method.. whoever no's feel free to speak up...
Yeah you take a pvc or pvc type pipe and a medium mouth funnel, place the pvc pipe in the tank all the way to the bottom, and place the funnel in the pipe not in the tank. then pour the sand slowly into the funnel and slowly move it around the bottom of the tank to spread it out. Then grrom with your hand to make it perfect. Key word here is slowly.
Another method is to put the sand in a plastic bag and cut 1 corner and make it like a pastry bag. Hold the cut end closed and the slowly put the bag in tank and release the sand.