I posted earlier about something in the bottom of my pool. I first thought mustard algae, but that is not it. Numbers are good, no FC loss overnight, no cc. Deep end is slightly cloudy. I then started thinking it must be sand, but it is fine particles that seem too small for sand. After doing some internet research, I am now wondering if it is residue from the Cal-Hypo I use. It is a brownish color though and in significant amounts on the bottom of the pool. UGH, I think it must be sand... IDK. We replaced laterals and sand last year. We used the right sand from the pool store and had no problems all last season.