It is entirely possible to have a CC of zero and still have an algae problem. Usually the FC won't hold overnight, though. Since you have so many issues with your water, and have posts all over the forum about it, it's getting hard for me to keep up with what you've tried and what you haven't. It would be a much better idea (and you're more likely to get useful information without repeats) if you would start one thread somewhere (or pick one you've already started) and stick with it until you get the water cleared up. It takes some patience sometimes for us to figure out the problem and give you a solution that works, and sometimes it's a trial-by-error process, but with some patience it will happen....but if you have multiple posts everywhere and are trying multiple solutions at once, you can easily go all summer before your water gets clear.

Janet