I use playground sand from home depot. I have it in 4 tanks right now, and two of those tanks have catfish with soft bellies, or cichlids that love to dig and play in it. I also have a freshwater Moray Eel that has an extremely soft belly and he seems to love it. I got mine for about $4 after tax and picked up a Home Depot 5 gal bucket as well. Dump the bag in the bucket, put your garden hose in there, (or removable shower head hose) and run it for about 20 min in nice hot water while thoroughly agitating the sand then just let the water run... Does a few things: Rinses out and chemicals left from manufacturing process, Smooths out edges of the grains by the agitation, and rinses away the sand "dust" that will cloud your water and plug your filter for weeks. Not to hate on anyone else's idea, but there really is no feasible need to mix with store bought stuff... If you cycle properly, the bacteria will propagate in the play sand as well as the LFS stuff. Another not, the sand is silica based and has shown no signs of P.H. increase or decrease...