I'm the original poster here. I have a 17,000 gallon pool and used ascorbic acid to remove the yellowing. About 10 days later the yellowing is starting to re-appear. So, as asvised I purchases some Jack's magic and am waiting for it to come in. The question that I have now is...how much of Jack's Magic should I have purchased. when I contacted Jack's Magic website, this is their response, but I wanted to check here before I bought more. I have one on quart on the way.

Reply from Jack's Magic...
"Jon you need to put 2qts of purple stuff in your pool.

Then you need to prevent them from coming back. You need to put 12 to 16
oz a week to prevent them. If you would like you may buy a sequesting
test kit for the correct amount of purple stuff you need weekly in your
pool. it takes 3oz to raise your level 1ppm. If you have anymore
questions I may answer for you feel free to call us Thanks

John Virga
customer service
(800)348-1656 EXT 111"

So, my question is, do you all agree with the response from Jack's Magic?

Thanks,
Jon