In a 25K gallon pool, each 2 gallons of 6% bleach will raise your FC by 5 ppm, so you can use that as a guide. As to how high your chlorine needs to go, that will depend on your CYA level. If you can see the blue links at the bottom of Watermom's sig, click on the "best guess chlorine" table to tell you how high your Cl needs to go, based on your CYA level. You can absolutely shock with bleach and still use your tabs in the floater, IF your CYA level is not too high--most folks keep it around the 40 ppm range.

Janet