I am a new pool owner and I don't know a lot about them. It is a 18x36 inground salt water pool. It is brand new. The people that put it in told me to bring in water every two weeks for testing. At first, they had me add salt, stabilizer and calcium. Then on the third visit, they told me that my free chlorine was way to high. They told me to cut my chlorinator to 10% for a few days to bring in down, then gradually bring it up a little bit. I turned it down and then turned it back up to 25% 2 days ago. I took water in today and they are telling me that I need stabilizer and calcium again. Can anyone tell me what causes this? Am I doing something wrong, or are they just trying to sell product? Thank you for any help in understanding this.