adjust cya before or after shocking

[Kateyru]

Glad to know it is very subjective test!

[Watermom]

It is definitely the hardest test to interpret.

[Kateyru]

Ah, you guys, I'm back again with green algae dust ): A quick recap of most recent battle with algae...from 5/21 to 5/24, FC was over 15 until afternoon of 5/23 when it dipped to 12.5 at 2:30 pm. CYA was at 45 during this period, fyi. I think that's when (on 5/23) we thought I'd won the battle, and I was letting FC drift down. Since then, the FC was below 7 only once on 5/28 and was at 5.5 when I turned SWG back on. On 5/29, FC was 7.5 and pH was 7.6. I turned SWG back off to get FC down to 5. This morning at 10:15 am (when I noticed green algae dust), FC = 5.5, CC = 0, pH = 7.6, Ak = 80 and CYA was about 65 as I started addingCYA again on 5/29 because I thought algae was long gone.
So, did I not keep FC over 15 long enough? How long is long enough? I think I had FC over 15 for a longer period than 5/21 to 5/23 but did not have reagent until 5/21 to know FC for sure. I know that I have to have FC at 20 now that CYA is up. Other thoughts???? Love my pool, hate the algae.

[chem geek]

Is your vinyl liner blue? If so, then I think you may have yellow/mustard algae and not green algae. Yellow+Blue(cyan) = Green. You describe the algae as "dust" which sounds more like yellow/mustard algae and would explain why the usual chlorine maintenance levels aren't keeping it away. Is the algae mostly on the wall and floor in the shady area of the pool? Yellow/mustard algae prefers shade. Do you have any removable ladders or other equipment in the pool where the algae might be hiding out inside? For plaster pools, we have people go behind light niches where they often find a lot of yellow/mustard algae if they have such an infestation, but I don't think you have pool lights (and therefore light niches) in your vinyl pool, do you? Is the algae in areas of poor water circulation?

Also, are you sure that it's algae and not pollen?

[Kateyru]

Yes, liner is blue. as i said on other thread, algae seems to disappear in the direct sun tho I think there is almost always a yellowish band of ??? algae (or a stain) where the wall and floor meet in several areas around the pool...if that makes sense. I have a ladder, not sure if it's removable as I've never tried to take it out. I have 1 pool light. How do I identify areas of poor water circulation? I'm fairly sure it's algae and not pollen.
Just read section on mustard algae, and I think you're absolutely right...that's the problem! No wonder my efforts were not enough. Sounds like a major production to get rid of mustard algae.
Many, many thanks!!!

[Kateyru]

Just realized that I posted a response on the other thread so left out some info here. CYA was about 65 on 5/30 so my shock level is now 20, correct? I'm going with the mustard algae theory so will shock at 20 till FC loss is < 1 ppm. Hoping that is done today (I was out of town all day yesterday and couldn't do much). When that's done, I'll move to super shock to get rid of mustard algae and will keep FC at or above 35 to 40 for 24 hours, correct? I've got to figure out how to get light out of pool. Can I put robotic cleaner and cloth bag, rubber mat (float) and nylon recliner floats in pool for 1 hour (in super shock) or is it better to clean with bleach solution? Also, instructions say to wash bathing suits. Do I need to use bleach with suits?

[Kateyru]

If I can't get light out of pool, is super shocking all for naught???