My tub is 330 gallons. My SWG is a bit different, it is part of the tub itself and has a setting from 1-10, I have found that 6 seems to keep it where I want it, although I did an ahh-some purge yesterday so I am curious if it will be able to run a little bit lower as I got quite a bit of gunk out which I am sure was chewing through some chlorine. I have found too, after the kids have friends over (and have the same scenerio as you), that cleaning the filters helps get things back in check as well especially the foaming.