Moved from here.
Quick follow up - is the point here to make sure the FC level is always above minimum #? Should I be testing throughout the day, like I did when I was SLAMMING? My plan is to test every evening, adjust to get the level up, run the filter for a couple hours... and repeat the next night. My fear is by doing that, the pool could potentially get below that level for a period of time during the day, and get algae again.It's all trial-and-error. Let's say you start at 5, add enough to get you to 7, and 24 hours later you're at 4. You didn't add enough; with CYA at 65, minimum FC is 5. You dipped below that. It will only take you a week or two to know your usual consumption. By the way, 65 CYA is not too high if it's real hot and sunny. Knowing your typical consumption, you can get lazy - we all do, eventually. You'll be able to skip testing once in a while and just dump in the usual amount. And you'll also be alerted if consumption suddenly goes up without a good reason, like a pool party with 8 6 year old boys or something.
They key is to add enough to keep the FC above the minimum for your CYA level until you can add more. Pool Calculator is your friend, bookmark it. Big party? Load up 2 or 3 ppm beforehand.