Hey everybody...first time here in while. My neighbors have what I estimate to be a 30X12 fiberglass inground pool. I don't have the particulars on pump filter and those things because well it's not my pool. However, they had pool guy come and take the cover off, and clean and "open" the pool yesterday. They put "some chlorine in and did some other stuff. They took a water sample because the guy found at the deep end of the pool about a three foot by twelve foot black spot. Ran the width of the pool and about three feet out from the side of the pool. I am guessing that this is black algae. Pool guy took a sample back to his LaBORATORY...and was supposed to call them today with results. In the mean time I used my trusty kit and did a quick test:
FC 1 ppm
cc 0 ppm
calcium hardness was 440 a bit on the high end
and Alkalinity was 70 too low.
Questions...is the black spot on the end of the pool black alage? it would not scrub clean for me...so I am guessing that the pool was not brought to a high enough FC level last fall and we a fairly mild fall and a mild then cold then hot then cold spring. So what would they use to clean the stain which is very dark, charcoal gray kind of color. The water is somewhat cloudy...and do they need to mess with the calcium level...and I know alk has to come up and I will verify on the pool calc how much to use. Thanks in advance for any advice. They said that they had spent close to $500 bucks last summer and I want to help them enjoy their pool and not get taken to the cleaners.