Hi all. This is the 3rd year my wife and I have had this pool and our grandsons love it. Last year when we opened the pool it was so green and nasty we drained the pool and started over. (didn't close it properly) But when we opened it this year it was much better. We first added PH up, then algaecide, then shock. Water was crystal clear after a couple of days. Then we couldn't keep chlorine in it. 5lb of shock only helped for about 6 hours then it tested no chlorine. 3 bottles of bleach helped for about 8 hours then it tested no chlorine. We finally broke down and had the pool store test the water. I will try to attach the report. We added 12oz of the phosphate remover last night but this morning the water is cloudy and there is a black circle in the middle of the pool about 3 feet big. I think it might be black algae. First and foremost, can someone please recommend a good water test kit? We have a cheap kit that we bought at walmart but it only tests the ph and chlorine. Before we add anything else, can someone please advise exactly what we need to do next? Thank you for your help.