This is our first year with our new pool and we already have some stains. I took the mesh cover off after winter and saw the rock and plaster had these stains on them. What is it and how can I prevent it? Is it something leaching out of the stone or mold/mildew/algae growing or what? The pictures don't show it but the stain in the pool runs directly under the stone. (The dark spots near the waters edge is just water drops)
Also, on a slightly different note and possibly should be a different thread: The pools been open for a little over a month now; I have a couple of small stains forming below the waterline blackish/browish very light, won't scrub off with pool brush. My FC dropped to 1-.5 a couple of times when I was trying to get my CYA under control (slowly bringing it up, 25-30 right now), but I've been on top of it lately with my FC 2 or higher and my CC never above .5 if they register at all. I've done a OCLT a few times and it shows no chlorine being used. Possibly algae? Should I slam to be sure? When the pool was originally plastered and filled, within a few day a streaking brown stain formed at the bottom of the deep end. The installers came out and took a hose and acid washed it away. I'm now seeing it has slightly returned. Is something pushing its way through the plaster and the small stains at the waterline the same thing?? Help.