I'd like to create "rolling hills" so to speak, in my 75g planted tank I'm putting together. But finding sand has been difficult, everyone has live sand. I found sugar sized aragonite at a store for $34.99 for 30lbs. And plain white sand for 5.99 for 5lbs. I would like white white, not off white. Suggestions on what stores or what kind of stores would have this? And how many pounds i'd need to have full bottom cover with a few elevated hills?