CC increase after mustard algae shock?

[FightingGobbler]

I’ve noticed that my chlorine demand has increased the past few weeks greater than past last few years at this time. Also, failed an OCLT. Water has a slight haze but no macroscopic algae. I’ve had mustard algae in the past (I think) that responded to a SLAM...but I didn’t complete the MA part in the past. I typically keep my FC at the upper limits (9 with CYA of 60).

So I decided to do conventional SLAM and followed by full MA this time.

Starting numbers:
FC - 1.5 (as I said, I usually try to keep this at 9 or greater)
CYA - 50-60 (I find it very difficult to get the CYA to 70)
pH – 7.5
CH – 375
TA – 70
Borate – 30
Salt – 2900

Dropped pH to about 7.3. Pulled out the pool lights, dumped all toys into the pool. Did a SLAM. Checked FC at least 4x/day and supplemented chlorine as needed. Brushed pool at least twice a day. Kept pool robot running and clean. Ran pump 24-7 and cleaned the filter once. Passed all 3 tests after 2 full days.

Now I’m almost 21 hours after initiating MA SLAM. Lights remain out of the niches and niches have been brushed. Toys still in pool. No ladders or water elements.

This morning, again 21 hours after starting, my FC dropped from 36.5 to 33 overnight (using OCLT technique) and my CC was 1. Is that typical? Does this represent killing of the mustard algae that could withstand conventional SLAM? Something else?

Should I continue MA slam for longer than 24 hours?

Thank you for any advice!

 

[ajw22]

Have you been brushing your pool frequently during the day? Brushing breaks up the algae biofilm and lets the chlorine attack it.

At high FC levels like you have a few ppm loss is normal. I would let your pool FC drift back down to your normal target level.

 

[FightingGobbler]

Hi Allen,

Yeah I've been brushing at least twice a day and keeping the pool robot going at least 4-6 hours/day. Also brushed out the light niches twice.

It was the CC of 1 that developed near the end of the 24 hour MA shock that was concerning.

I'm going on almost 36 hours of MA shock levels now. If it holds by morning, I'll let it drift back down.

Btw...you had answered a question I had a few months back about getting a Hayward inlet eyeball removed. Life happens...and I didn't get a chance to thank you before the thread was closed. So thank you twice!