Mustard algae

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Eric K.

Bronze Supporter
Apr 18, 2016
60
Hilo, HI
Reposting this from yesterday...I have struggled with mustard algae this year as well...

First, a couple questions:
- Does MA show up on the CC test? I've had the dust all this year, and even after brushing it up, I would still get 0.0 CC.
- I saw somewhere (here?) a different FC minimum for MA. It is 3 to 4 ppm higher than the minimum I was watching for years. What is this about? Do you target the higher number once you've had MA?

For over a year we've had the dust (FYI...we don't winterize pools here in HI). I always thought/hoped it was pollen, but after a slam (@ regular slam levels) it would reappear after several days. First on walls, then slowing forming drifts on the bottom.

A few weeks ago I decided to slam for MA for the first time. Brought it up to MA slam level, and after a couple days dropped robo-vac, hoses/head, brushes/nets, toys, everything I could think of, into pool overnight when at slam levels. Brushed daily. There's no ladders or lights, just 3 plaster steps and a steel handrail going in. Pump ran 24H for seemed forever, nearly a week. Passed the OCLT 2 nights in a row (but, does MA show up on a CC test?).

Since this last slam, it was gorgeous. As sparkly clear as it's been in a long while. For a couple weeks. Then, today, on a swim, I see a little bit of dust at the bottom. Then, check walls, brush, and sure enough, its back! Its minimal, but, I thought I was done with it! I vac'd to waste, then brushed, and will vac to waste again tomorrow.

Here's the numbers:
This evening:
FC 7.5 (hours after adding 2 gallons 10% following "discovery" swim...but I hadn't been watching the MA minimum just the regular target which is below the MA minimum!)
CC 0.0
2 days ago:
pH 7.5
TA 70
CH 225
CYA 30

I'm dreading another MA slam, and certainly don't want to do it the same way if it was wrong last time, or if I'm supposed to be following a higher MA FC min/target once done.

Is there any hope that the higher MA FC minimum will take care of what has returned? Or, what do I do with that MA FC number? Is another MA slam imminent?

Thank you!
 
Just because it returns does not point to mustard algae. Mustard algae is misdiagnosed more often than not. Got a pic? Does it grow on the shadt walls of the pool?

Always remind yourself that algae simply does not grow in the presence of adequate chlorine. It can grow if you fail to brush properly because it can find a little niche in the surface and form a protective biofilm over itself as a shield from the chlorine. However, the most common cause is letting your FC get too low for too long.
 
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There really isn't a shaded side of the pool, except morning and evening tree shade on different sides. This stuff has appeared on all sections of the wall at different times. It brushes off very easily, then clouds up, then settles into drifts on the bottom. It moves around with the slightest water movement. When its bad, and I slam, brush, and run pump, my filter socks turn green. Much of it passes through the sand filter unless I put in close to a cup of DE.

Since I brushed yesterday, there's nothing to take a picture of.

My question remains...after my MA slam, should I have tracked the MA FC minimum instead of my regular FC min? If so, maybe that's why its back?
 
My question remains...after my MA slam, should I have tracked the MA FC minimum instead of my regular FC min? If so, maybe that's why its back
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The short answer is I don't know. I have yet to see good evidence for mustard algae but I am not there. Do some research on this forum and look at pics of mustard to see if you can clearly identify it.

If it was my pool, I would elevate the chlorine to perhaps 50% more than maintenance level for the next few days and brush daily and run your filter 24/7. That should take care of it.
 
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Moved from here.
@Texas Splash I have a couple questions.
If there's no OCLT for MA, does that mean it doesn't read on FC and CC tests? Because, if you've passed the OCLT then up it to MA levels....there's still MA in there?
Also, do you know why MA has a minimum FC that is 3-4 ppm higher than normal FC? Is this about managing the MA you can't rid yourself of unless you raise to MA slam?
 
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