I am in the process of purchasing a house with an inground fiberglass pool, built in 1981, approx 25,000 gallons, located in Albuquerque, New Mexico (full sun all day). It has a gigantic sand filter that is as old as the pool itself, not sure of the pump brand/hp just yet. The who owns it right now uses the chlorine pucks in the skimmer basket so I'm sure the CYA is sky high and I will need to do a partial drain once I take over. Otherwise he just takes water to the pool store and does whatever they tell him to do, but he tells me the numbers are all decent. He does leave a solar cover on it all the time to heat the water, which might be contributing to the cloudiness. I will have a T-100 test kit here by the time I take over the pool. Right now, the water looks okay, is a nice bright blue, but it's a little hazy/cloudy. I'm wondering if that will clear up with proper attention and testing and leaving the cover off some, or if that's something that will really only go away with a SLAM. My main priority is to be able to swim ASAP, can you still swim in the pool while doing a SLAM?
Pics of the current water condition, picture with the stairs was taken in the shallow end.