Hi All, I'm new here. My pool was clear until a week and a half ago, when it turned quite cloudy and even a little brownish/greenis and I've been trying to clear it up ever since. There seems to be a lot of whitish/brownish debris in the bottom that clouds up when I brush it, which I am hoping is dead algae. However, when I vacuum it, it seems to shoot right back into the pool as though the filter is not catching it. I have a cartridge filter, which i have cleaned several times. I'm keeping the chlorine level high using liquid chlorine, but I haven't been able to get the proper test kits yet to properly SLAM it. Does it sound like I need to replace my filter cartridge? We switched from a sand filter to this one in 2018, but I've never replaced the cartridge, only cleaned it. It was worked great up until now. I'm not sure if its the cartridge or the fact that potentially let algae get out of control.