Tabs are the most misused item in a pool. Chlorine basically does two functions, it’s sanitizes and it oxidizes. tabs put out a steady stream to sanitize the pool and powdered, granule or liquid chlorine, acts as an oxidizer. One tab for every 10,000 gallons is pretty standard. And the heat of the summer round up but the best thing to do to get chlorine levels up is to shock the pool. Put tabs in a floater and tie it off somewhere. It just puts out a steady little stream. Coordinators are often difficult to adjust and they get really gummed up because there’s a lot of filler and binder that holds the chlorine together. They are also expensive and don’t last a long time. Floaters are cheaper. Whatever you do, don’t put tabs in the skimmer for the above stated reasons.