Start at the grocery store for lots of bleach. :grin: Since you don't have any test results and everything is green, we'll assume the worst, so do the following:
(FIRST - Adjust pH to 7.2) Then ........
1. Begin a SLAM and dose FC up to SLAM level. If your CYA test is showing as zero (perhaps already converted to ammonia), use a SLAM/Shock FC of 10. Do not add additional CYA at this point.
2. Retest FC at 10-minute intervals.
a. If FC loss is greater than 50%, add FC to bring back up to SLAM level and continue retesting FC @ 10-minute intervals.
b. IF FC loss is 50% or less, add FC to bring back up to SLAM level. Go to Step 3.
3. If CYA is below 30 ppm, add enough CYA to bring level up to 30 ppm.
4. Continue SLAM as directed in the SLAM article until the SLAM Criteria of Done are met. Test as directed in the SLAM article - no longer need to test FC at 10 minute increments at this point.