Technically, you can run as little as you want to as long as you meet the FC targets in all parts of the pool but when dosed manually, this usually requires less than an hour of run time. Other methods of chlorination could take longer.

During the heat of the summer I run 4 hours per day with 3 of those hours on low speed and never had any water problems. Currently I am running only 1.5 hours total and the water is as clear as can be. Some people can run even less than that and one person on another site has gotten his run time down to 30 min per day.

But I would argue that sparkling water really has nothing at all to do with filtering. Even the best filters can only filter down to about 5 microns and particles of that size will either float or sink. In order for particles to be suspended in water and affect clarity, they need to be smaller than about 2 microns. The filter is there mainly to trap larger debris that float into the skimmer or are vacuumed from the pool floor. Particles suspended in the water, pass right through the filter.

But what really should determine run time, is the tolerance for the debris on the pool floor and on the water surface. This is the main function of pump run time and filtering besides pool heating.

Have a read through the pump run time study in my signature. During their testing, they saw no significant improvement in water quality after 2 hours of run time. This has been my experience as well.