It depends on your starting CYA level, how fast you have the floater set to erode, and what levels you consider unacceptable. MOst people like to shoot for the 20-40 range. Others run theirs higher. It all depends on how much chlorine loss you have on average, and how diligent you are about daily chlorine additions. The tabs will continually drive your pH down, so if you're already having low pH problems, I would skip the tabs and stay with bleach.

Janet