Turning green, but FC is good...metals?

[gilbee]

I did an AA treatment of my water at the beginning of February; it made a huge difference as the plastics has turned brown from iron over the season since the replaster. I used polyquat to buffer the pool while I had the chlorine at 0, and things stayed clear. I've since started to rebalance the pool, and things are going fairly well by the numbers:

3/5/2016
FC 6.5
CC 0.5
pH 7.7 ( I added some acid to bring it back down to 7.5-7.6)
TA 80
CH 350
CYA 0-20
Borates 50 (Carryover from an old test)
Sequestrant 14 (taken with a magic Jack's sequestrant test drop kit)

Over the past couple of days, I've noticed the water turn green in the pool, most noticably in the late afternoon. The water is still clear however. I don't know how the CYA dropped, as I have a reading within the last month of 50 and I had added additional CYA to get me closer to 70-80. Water temp is in the 60s, but I wouldn't think that would cause a false reading this far off...does ascorbic acid, polyquat, or the sequestrant have any possible role in this?

Here are some pics (imgur link)...am I looking at the beginning of algae, or is this a metal thing? I remember when they first filled the pool after plaster, the water turned a green color like this, and they added a sequestrant (super sequa sol) and the water stopped being green. Obviously I need to add CYA, but what action shoudl I take to remedy the green tint? Notice in the last pic the difference between the pool water and the spa water. The spa is overflowing into the pool, and the water that is causing that overflow is being pumped from the pool, so I would think if it were algae, the spa would be turning green too, along with a high CC which simply isn't present...

- - - Updated - - -

Also worth mentioning, the pollen has started falling here...

 

[Swampwoman]

I personally can't tell from your pics. What measurement of jack's per the test do you normally get to have water sequestered? If the problem s metals, slamming will exacerbate, so why not top up your sequestrant level first to see if it clears, run your cleaner to see if its pollen, and if neither bring you to clear, then slam.

That's pretty much the order I would try to troubleshoot because I have known metals, as do you.

My other thought, which might be wildly inaccurate, is that I am wondering if your cya is lw, the strength of the chlorine is therefore not buffered, so perhaps somehow 6.5 FC is oxidizing the metal. That doesn't in my pool, but I've not ad cya that low and Im not on swg. In this scenario, I'd be inclined to get the cya up if you're really really certain of that reading.

As to where your cya might have went...cya will convert to ammonia if chlorine drops to zero. I don't drop o zero when doing AA treatments...I just historically kept it lower than usual. But not zero.

So, many mysteries here, but from where I'm sitting, you might need to do a bit of trial and error starting with simply adding sequestrant, bringing cya up a bit, then observing outcome.

 

[pooldv]

Ascorbic acid can use up FC and left with little or no FC bacteria can consume your CYA. I would perform an OCLT first to see if there is algae, Pool School - Perform the Overnight FC Loss Test (OCLT)

 

[gilbee]

All good ideas...since the sequestrant is already at 14ppm, I'm hesitant to add more since the normal range is closer to 10ppm. I will do another CYA test tomorrow late morning, and if the reading is consistent, I'll add CYA to get me back toward 70. OCLT will also happen tomorrow evening to see where we lie.

 

[gilbee]

So, I tested again with a new bottle of CYA reagent, still got 20 so the reading must be good. Added half of the CYA needed to get me to 70, will recheck in a few days and then add the rest. I don't want to add the whole amount now simply because it will cause a 1.1 drop in pH if I add it all at once, and I'd rather let it drop to a still acceptable level for my equipment and use the addition as a way to keep my pH in check which I'd be doing with MA anyway. I may wait until tomorrow for the OCLT.

 

[pooldv]

Good plan!