check out any sand blasting places. someone i know locally got about 200 lbs of it for $60 canadian, so like $50 american. it's not treated with anything(but be sure to ask them) and it doesn't need to be rinced that much. they had other colours there as well, white, brown and beige. they also had a couple different grit sizes. you could also check out landscaping places and see what they have available. the package should say what it is and if it's treated with anything, then you can check it out online and see if it's safe for aquarium use.