I agree that mineral systems are a supplemental sanitizer and will not sanitize the water completely but they do help. Also, I agree that there are only three sanitizers - chlorine, bromine and biguanide. Of the three, chlorine is the best and the most economical. Natural minerals, however, such as silver and copper, have been used for thousands of years to effectively control bacteria, algae, and other harmful contaminants. A residual sanitizer is needed, in a pool, that has a fast kill time. Chlorine is the best alternative and a salt water chlorine generator is a great way to supply that residual sanitizer. I'm just trying to use a blended system.
I'm under the impression that lower CYA levels promote better FC effectiveness. People who follow the TFP principles want to preserve as much chlorine as possible and would probably want higher CYA since they may be skipping a day since they last added any chlorine. With a SWG, I am putting chlorine in the pool during the daylight hours when the sun is up. A good analogy is a comparison to treatment for Diabetes. In the past and now, people gave themselves shots each day to keep their insulin under control. There would be ups and downs. Now, there are new treatments and implant pumps that allow the insulin to be given in a measured dose all day instead of in one shot which avoids the large swings in blood glucose levels. The comparison to SWG insertion of chlorine in measured doses is obvious and is the reason that people say salt water pools are superior. In public pools, obviously, there have to be laws governing the type of sanitizer used but in private residential pools there are no laws. I am just trying to find the best system overall.
This is a great website and resource. The TFP methodology is solid and is a great system that helps to develop and promote a simple, inexpensive, and effective system of pool care.