SLAM worked (I thought?) but algae is back...


New member
Jun 10, 2016
Round Rock, TX
Pool Size
Salt Water Generator
SWG Type
Hayward Aqua Rite (T-15)
Hi all - first thread for me... I've read a ton of threads on TFP about mustard algae and SLAM experiences, but I haven't learned enough to understand the situation I'm in now. I've been wrestling with what I think/thought was mustard algae, for a long time now. I finally rediscovered TFP and the SLAM method a week ago, and here is my experience:

  • Recurring accumulations of yellow/brown sand-like stuff. Not climbing up walls, that I could see. Easily brushes off into a cloud. I'll attach photos.
  • Pre-SLAM measurements (using TF-100 kit)
    • FC ~= 8.5 ppm
    • CC ~= 0.5 ppm
    • CH ~= 575
    • TA ~= 80
    • CYA < 20
    • pH ~= 7.4 (was 7.8, lowered it just before starting SLAM)
  • Cleaned out filter and cartridges

  • Targeted FC of 16ppm (not trusting my CYA measurements... Leslie's pool store told me it was 50 a week before. No, I don't trust them either)
  • Turned off SWG
  • At first, I somehow overshot FC by a ton... measured 31ppm the evening of day 1.
  • SLAM lasted 4-5 days. Checked FC and added liquid Chlorine as often during the day as I could. Very sunny here in Texas right now, and as expected with low CYA, it took a lot of additions. FC never got lower than ~11 ppm at any point.
  • CC never measured above 0.5 ppm
  • Each morning I'd see new accumulations of algae, but they were getting smaller each day.
  • On day 4 or 5, I learned about checking in light fixture niches. Found a nice stockpile of algae in both. :oops: Vacuumed and brushed them both out, left light fixtures out and floating, continued SLAM
  • On the 6th morning, I decided that the slam was complete:
    • OCLT finally passed (held at 17 ppm overnight)
    • CC was 0-0.5 ppm
    • No new algae accumulations - woohoo!
  • Following TFP mustard algae guidelines, I raised FC to 20 ppm for 24 hours.
Family got into the pool yesterday: lot of fun, dad's our hero, he beat the evil algae!

Then, I come out this morning... to new algae accumulations. FC is sitting at 9 ppm.

Any suggestions on what I might be missing? Looking at the photos... is this mustard algae I'm fighting? I was recently informed on this forum that mustard algae will climb walls, which I have never seen my algae do.

Many thanks in advance, and happy father's day to all!


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Mod Squad
LifeTime Supporter
Jan 17, 2012
Evans, Georgia
Why and How are you running such low CYA? I wonder how your pool is keeping much FC with such low CYA?

It doesn't sound like mustard algae to me, but rather dead algae. Mustard algae is found on shady areas of pool, on walls, etc. Can you pick it up or does it poof away?

How long do you run the pump daily, and what is your SWG setting??

Have you looked at cell to see if it needs cleaning?

Please raise your CYA to 70ppm. This would2 take 147 ounces of dry granular stabilizer (put in socks hanging over into pool water to dissolve) or using approximately 2 full gallons of liquid stabilizer (making sure to get all the sludge of CYA out of the bottom using water).

Maddie :flower:


Gold Supporter
Aug 20, 2020
Knoxville, TN
Pool Size
Salt Water Generator
SWG Type
CircuPool RJ-60
It looks like it could also be something washing into the pool from the deck? Your tile seems to have some similar colored stuff on it. Any chance some rain or other water is washing dirt or dust into the pool?
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