What is the stabilizer for pool water?

Dilution. You have to remove the overstabilized water and top-off the pool with fresh.

Try it in a test sample first. Fill a cup, pour out 25%, top the cup back up with fresh non-pool water and retest your stabilizer level. If that's not low enough, try 33% or 50%. This will tell you how much water you will need to replace in your pool.