Even though a FC reading of 7 sounds high, for a pool with extremely high CYA, it is not. In fact, it is too low. You need to be keeping it between 8-15 ALL the time. Dropping below that is an invitation to algae. In your pool, each gallon of 8.25% bleach will add about 2.8ppm of chlorine. I think if it were my pool, when I tested in the evening, I'd add enough bleach to take it back up to 15ppm. The next evening, if you have dipped below 8, I'd take it a little higher. You want to add enough bleach so that you can make it to the next evening without going below 8.

But, first we need to determine if you have an overnight chlorine demand. If you do, it means you need to be shocking the pool. So, go ahead and try the overnight chlorine loss test I described in my previous post. Report your results back tomorrow morning. If you felt slimy, your pool is probably on the verge of an algae bloom.

Also, bump your ph up with some Borax.