Thank you both. I didn't get much education when we had the pool installed 3 years ago. Just a pentair test kit, chlorine tabs, baking soda, muratic acid and a huge bill. The pentair test kit seemed fine until I developed some sort of algae a few weeks ago. It actually looked like a rust stain at first then morphed into what looked like a clot of dirt stuck to the bottom then it started spreading. I am assuming it's black algae but the color is still rust so maybe mustard algae. So, I headed to the only pool store in my town and they had me shock it and add an algae killer which did nothing except cause my pool to foam and develop a weird green film on the water line of my filter baskets. We have brushed, scraped and rubbed with a chlorine tablet but nothing has changed. So, after reading a few posts her I decided maybe I better order a different test kit and see what is really going on with my water. Until I get the Taylor K2006 kit that I ordered I don't feel comfortable dumping bleach in because my current test kit only goes to 3.0. I have never tested anything other than chlorine, PH and alkalinity. I am confused about all the other tests mentioned in posts. Hopefully, after doing some additional research on the boards I will be able to find out what else I need to be doing!