Borax

Thank you. We try. Our pool is always nice and the water has a good smell to it.

All this begs the question though --- What is the criteria for shocking the pool?

You do not routinely need to shock the pool. I only shock if I see CC (which is practically never) or if we have had a really large number of swimmers or if there has been a lot of rain that put a lot of organic debris in the water. If you maintain your water chemistry, you really don't have to shock the pool. I don't think I have shocked at all this season. (Unless I did it once early in the season and have just forgotten.)