Hi
And welcome to TFP. you have came to the right place.
The pool guys are wrong on every level and so is any advice or product from the pool store as well as pool store test results. They are horribly in accurate.
It can come off of there, but its a process, not a one or 2 time treatment. There is no miracle cure.
You will need to use liquid chlorine to solve the problem. Either regular household bleach without any anti splash or foaming additives or any of that stuff. Just regular bleach.
Liquid Chlorine pool shock will work too.
You will need to test the water and add chlorine several times a day, so you'll need a good and reliable test kit with a FAS-DPD chlorine test and a CYA test.
we recommend either the TF100 or the Taylor K2006. The TF100 is the best bang for the buck.
The Taylor K2006 is available several places online. The TF100 is available at only
TFTestkits.net and
http://www.pool supplyworld.com on the west coast.
once you have the test kit, you need to test all of your water parameters and post them here if you have any questions.
After that, adjust your pH to 7.2. Test for CYA and determine what that is, then use the below FC/CYA chart to dermine what the FC level wil be for the SLAM
then start the SLAM.
Pool School - SLAM - Shock Level And Maintain
Use pool math to determine how much of something you need to add for pH adjustment and chlornie addition to keep your FC at slam level.
http://www.troublefreepool.com/calc.
Pool School - Chlorine / CYA Chart
Pool School - Recommended Levels