I thought I understood what the target FC levels meant, and I know the specific numbers are related to your cya level, but the more I think about it the more I think I need a clarification.
I'm assuming that you should shoot to keep your FC at the the "target FC" number and never let the FC drop below the "Min FC" number. Does that mean that there is a good chance of algae (or any undesirables) growing between the target number and the min number? Also there is a Yel/Mstrd Min, which is always higher than the Target FC number. Does that mean that all (or most) types of algae would not grow if the level was kept at the target level, but mustard algae could grow at any level below the Yel/Mstrd level? And since none of us want mustard algae, wouldn't that make the Yel/Mstrd level the DEFAULT Target FC level?
Also, the shock levels....if we keep the correct target levels we shouldn't need to shock regularly correct? If a certain chlorine level kept stable will not allow most algae growth and/or mustard algae growth, why does it take such an incredible FC level to kill it off if it once it blooms. The Shock FC levels are about 3.5-4.0 times the Target FC level on average.
Also, would the answers to these questions relate to the idea of breakpoint chlorination, which is simply raising the FC to a level of 10 times the CC level. So if you had a CC level of 0.2 raising the FC 2 ppm could be considered a shock? (Chemical Shock - Shocking Your Swimming Pool | The Swimming Pool Library I also read about breakpoint chlorination in the Taylor 2006 instructions) And why is it that the pool industry recommends shocking once per week anyway? Is it that the average FC levels throughout the week keep most of the algae at bay, but not all, so shocking once per week makes absolutely sure nothing is growing? Or is it based on the fact that most pool services only visit a pool once per week so "shocking" it every or most times they visit is the standard?