I have been reading on here all about this topic. I understand that it is like a sunscreen for pools and it retains some chlorine, which helps to keep chlorine levels from going all over the place. My question is this: What does it matter if it helps retain chlorine if that chlorine is unavailable, which makes it useless other than to show up on ones pool test? It also requires that chlorine levels be kept higher, so I'm not quite sure how this is realistically helpful. Please explain!