For those of you who like to use sand as a substrate, I ran across a cheap alternative to pool filter sand while shopping at Toy R Us yesterday. I purchased a sand box for my boys birthday, they asked me if I wanted sand, only $5 a bag. Sure, saves me a stop at the hardware store. This sand would work great in an aquarium, it is white, nice fine grain size clean. Out of curiosity, I put a few lbs in a bucket and ran water through it, it is very clean, no rinsing required. I would assume most of the Toys R Us stores would carry the same thing.