I've been maintaining my own pool for about a month now (builder threw in 1 month free) and had my water recently tested at a local pool shop. They told me that my CYA level was 0 and sold me a bucket of CYA. I've read as many threads on CYA I could find but couldn't find the right answer to my question. I have a SWG and when I run it at 40%, the FC reading is stable around 1-1.5 ppm. When I increase it to 45%, FC reads consistently around 2-3 ppm. So my question is do I really need to add CYA when the FC reading seems to be stable? Thanks in advance.