Can someone please assist in identifying what this stain is. These stains are strictly in the deep end of our 6 lane, 25 yard, 165,000 gallon pool. The stains appeared about a month ago and haven't necessarily gotten any worse. It looks like sand at the bottom of the pool but of course when we go to vacuum or wire brush at we can't remove anything.
Chemically the pool is fine, just the calcium is a little low.
Any help is appreciated.lap pool stain.jpg