Ya, you did not screw up big time. That would be letting it get way down. Try your best to keep it at or slightly above 12. Make sure you are testing for those CCs too.
Also find any little nooks and crannies algae might hide. Ladders are a big place. Behind lights too, but that is more of a inground type of issue.
Also find any little nooks and crannies algae might hide. Ladders are a big place. Behind lights too, but that is more of a inground type of issue.