I don't think this point is emphasized enough in the pool school. About a year ago, as a new pool owner I thought clear water is all about chemistry. I had all the kits, I was measuring chemicals once a day, SLAMing regularly, calculating values, keeping things within .5 ppm of targets. I spent a lot of time and money, and my pool was at best cloudy and at worst green. Until I replaced my small, old cartridge filter with a big DE filter. BAM! since then I just add some chlorine every once in a while, test water maybe once every 3 weeks, and water is clear as mountain springs!