Yellow walls are back with a vengeance!

[Flyguppy]

Apparently I was not successful with my first mustard algae SLAM last month.

Quick question....

Is there any reason I cannot go straight to M.A. SLAM level instead of doing a normal SLAM first?

 

[Abigail K]

Normal SLAM instructions have been tweaked over the years to give the best algae-killing without bleaching the pool.
Chlorine loss is a percentage of starting chlorine levels, you lose more chlorine going straight to M.A. SLAM levels.
The recommendation is to do a normal SLAM until you pass all 3 criteria before taking the pool to M.A. levels for 24 hours.

 

[Flyguppy]

Is it possible for me to be having just a .5 FC loss on the overnight chlorine loss test when I have what I believe to be mustard algae?

I have yellow on my walls if I go a day without brushing them. My steps have significant yellow/brown clouds when I sweep them every day. It's got to be algae, right? If it were pollen, it wouldn't collect on the walls, correct? The pollen season is long over here in Houston.

I went from 6.0 FC to 5.5 overnight. No CC.

CYA - 45
TA - 180

 

[Diver]

I've been having greenish-yellowish spots here and there for quite a while as well. I just finished doing MA SLAMing and the levels are still coming down and so far everything is clear.

I also had a negligible FC loss during the spots appearance. With a solar cover on 80% of the pool, I would sometimes lose only 0.5ppm per 24 hours even though I had visual signs of algae. The spots might be attributed to poor circulation, but I would think it would still show up on the daily FF loss.

The time line of shocking is also interesting:

8:00 pm - starting shocking, initial FC 7.5, target FC (calculated) - 24.7
9:30pm - FC: 23 (1.7 loss, some of it might still be due to UV, some to organics, the estimated 24.7 might be off a bit due to water level, etc)
6:00am - FC: 22.5 (0.5 loss, sun was partially out already), CC:0

So I basically passed the OCLT right away and started MA SLAMing the same morning.

So I would have clear water, no CC, minimal FC loss and some visible green-yellow spots..

 

[JasonLion]

Low levels of mustard algae can sneak past the overnight FC loss test. Once it gets going the chlorine loss will be obvious.