I have the test kit from walmart but i will order the other one tomorrow. thanks for the info. i did power wash my cartridge today and soaked it in clorox, plus shocked the pool. my PH levels are very low so will get that as well.We have had our pool for 20 years and this is the first time we have encountered this .The reason i asked about the sand was that is the only difference in what i do every year.We put new steps in the pool and weighed them down with sand.So i will get back to you once I've done the steps you have suggested.