I have a 5 gallon bucket FULL and ended up throwing away about 1/4 of a bag! My tank doesn't use much at all but it is softy dominent. 50 lbs goes a long way for sure. Thanks APfish but I just needed the directions for quanities and bake time for the soda. I have read that dow makes it, packes it, under differant names. I think the dow is only 90something % pure also.