Stabilizer is CYA is Cyanuric Acid.
Originally Posted by mommark
As it says in Pool School - Recommended Pool Chemicals which I linked before
CYA - Cyanuric Acid
CYA can be raised with cyanuric acid. Cyanuric acid is sold under a variety of names, including Stabilizer, Conditioner, Instant Pool Water Conditioner, Stabilizer 100, Stabilizer & Conditioner, etc. Instant Pool Water Conditioner is a liquid product which is significantly more expensive than the other forms.
Solid cyanuric acid should be placed in a sock, and the sock put in the skimmer basket. After adding solid cyanuric acid you should leave the pump running for 24 hours and not backwash/clean the filter for a week. Solid cyanuric acid can take up to a week to fully register on the test, so it is best not to test the CYA level until one week after adding some.