You use bleach to chlorinate when needed, to keep your FC at the recommended level. See below.

Ben's 'best guess' FC/Stabilizer table for algae free operation of OUTDOOR pools -- as of July 2003 --

Use the info in this chart to help you figure out what levels of chlorine you need to maintain in your pool based on the amount of CYA (cyanuric acid, also called stabilizer) that you have in your pool. (FC = free chlorine)

Stabilizer . . . . . . Min. FC . . . . Max FC . . . 'Shock' FC
=> 0 ppm . . . . . . . 1 ppm . . . . . 3 ppm . . . . 10 ppm
=> 10 - 20 ppm . . . . 2 ppm . . . . . 5 ppm . . . . 12 ppm
=> 30 - 50 ppm . . . . 3 ppm . . . . . 6 ppm . . . . 15 ppm
=> 60 - 90 ppm . . . . 5 ppm . . . . . 10 ppm . . .. 20 ppm
=> 100 - 200 ppm . . . 8 ppm . . . . . 15 ppm . . .. 25 ppm

So, your CYA is 90, therefore your FC reading should be between 5-10 ppm. Nice thing with a high CYA, it will hold the chlorine longer. Still, if you've only started using bleach, I'd advocate testing nightly just so you get a feel of how your pool holds chlorine. I know that I need to add a large jug of 6% ultra bleach every third day as maintenance. But, add more following heavy usage. I add the bleach thru the skimmer basket. No extra gizmo's needed to do this.

Hope this helps.

CaryB
Go 'Canes!