Hi, Greg,

For a plaster pool and CYA of 80, I'd put in enough Cl to get to 30ppm.

You'll surely get to breakpoint and clean up any "bugs" that may try to establish themselves.

If you have mustard algae, you can maintain that shock level for a few days, brush frequently and run your pump 24/7. Pooldoc advises that mustard algae takes high Cl and a lot of persistence.

After that "shock", you can let your Cl drop on down to 5-10ppm and keep it in that range the rest of the Summer.