Left C is right. Some of the pool filter sand sold is more a cream color than solid white color. Estes makes a pure white marine sand that (as stated on the package) is supposed to be safe for fresh water planted tanks. I have no experience with it but I know Waterfaller uses it, so hopefully she will chime in about her experiences with it. It is not as cheap as pool filter sand. IME, I have used pool filter sand and am not convinced that the high silica content gives ongoing diatom algae. The diatom algae that I got when I set up a tank using it, lasted only 4-6 weeks which is normal for any new setup, and a otocat I put in the tank made short work of it. It was never an ongoing problem algae.