stain removal

tell me what i done wrong and how to fix. i had stains on my pool and i used the asboric acid method to remove. chlorine was at zero when i done the asboric acid. the stains vanished just as instructed. the pool was perfect. the next day i added bleach to start to bring the chlorine back up and everything still good. two days later, today, i notice the pool started to have a green tint. i added polyquat, and more bleach as the chlorine was showing very little. one thing i did forget to do is add metal out. is this what i done wrong? should i add metal out now?? the only other thing i done right after i used the asboric acid was to turn on my heater. did that have an effect on it? i have a 21,000 gallon inground, sand filter. please tell me what steps to take to get the pool back on track. thanks.

You most definitely need to add a sequestering agent (metal out) while doing an ascorbic acid treatment. The ascorbic acid lifts the stains off the surface of the pool, but if there is no sequestering agent (which holds the metals in suspension) the metals will fall out onto the surface as soon as you add chlorine and have your ph above 7.0 You can probably lift the stains by taking the ph down to 7.0 and adding sequestering agent - I find that you need more than the bottle says, so use some extra. Put the pump on recirculate for a couple of hours and see if it works.

If you have algae, I would shock before and get the water sanitized again before worrying about the stains. I would add some algaecide too. If the sequestering agent alone doesn't work, then you will have to add some more ascorbic - but not as much this time. Try a little at a time and keep the pump on recirculate until the stains are lifted. Don't forget the sequestering agent!