I don't have a multi speed pump, but I'm running my swg at 50% for 6 hours and my fc has come down 1.5ppm over the last several days. It had been 10.0 before I reduced the %. I'm trying to get it down to 5ppm before changing it to a maintenance level. I believe that I should be able to run it at 80% for 8hrs max during the summer. But, I'll play that by ear as the summer progresses. One of the pool stores I used to take my water to be tested insisted I needed to run it for 12 hrs when all it was doing was circulating the water. That seemed outrageous to me so I never ran it over 8 hrs. They also were trying to get me to buy $100 of their supplies to keep my pool nice. I laughed at them and continued to add baking soda to increase TA, borax to increase pH -- neither of which I've needed since going to bleach, got a decent testkit that I found my ta in my tap water was 120ppm, and put an aerator in my pool. Now that I have a swg the aerator is no longer necessary either.