Ugh, mustard algae again!

CrisH

Member
Jun 1, 2019
5
Marietta, Georgia
I inherited a pool with mustard algae. It's been mostly trouble-free until the algae comes back. Last year we were lucky to only have one bloom, in August. It's hot and humid here in Georgia. This year has been particularly hot and rainy and I'm onto my 3rd bloom, ugh! Anyway, last time I treated it with Yellow Out, then shocked it with 12 pounds of 73% cal-hypo (4 lbs every 12 hours like the pool store told me). I did that last year and it worked great. No more blooms after that. But this time it hasn't worked. Two weeks later, when the chlorine dipped a little too low (I pour liquid chlorine every night), the algae is back. This time I poured 10 jugs of 6% bleach (128 oz. jugs) like the Pool Calculator told me, to raise the FC to 29. I poured them all in last night. Do you think that's enough or do I have to do another 3-4 lbs of shock tonight for good measure? I've been vacuuming and brushing as well. I'm getting a good arm workout :/ Any tips appreciated, thanks! :)

P.S. the water is clear and blue.

Vinyl pool, sand filter, 27,000 gallons

These are the numbers prior to treatment:
FC - 5
CH - 160 (low, I plan on raising it after treatment, or should I have done that before?)
CYA - 50
TA - 80
PH - 7.7
Phosphates - 100
 

justinc

Gold Supporter
Apr 3, 2019
591
Texas
Hi, welcome. It seems that you are doing one time "shocks" here and there and hoping to kill the algae. In order to completely eliminate the algae, you need to follow the SLAM process. SLAM - Shock Level and Maintain - Trouble Free Pool

You have to hold your chlorine at shock level for your current CYA until you meet all the requirements to stop slamming. Otherwise the algae that didn't get killed will just grow right back once you let the chlorine level drop down....

Also, it is safe to ignore your low calcium hardness level in a vinyl pool. Don't worry about calcium at this time.
 
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CrisH

Member
Jun 1, 2019
5
Marietta, Georgia
Hi, welcome. It seems that you are doing one time "shocks" here and there and hoping to kill the algae. In order to completely eliminate the algae, you need to follow the SLAM process. SLAM - Shock Level and Maintain - Trouble Free Pool

You have to hold your chlorine at shock level for your current CYA until you meet all the requirements to stop slamming. Otherwise the algae that didn't get killed will just grow right back once you let the chlorine level drop down....

Also, it is safe to ignore your low calcium hardness level in a vinyl pool. Don't worry about calcium at this time.

Thank you!

I bought the FAS kit and measured the FC and CC levels this morning. It’s my first time doing it so I hope I did it right. I *think* I am done. In any case, we are leaving town next week so I’m putting tabs in the chlorinater and I hired a pool person to maintain once a week. Fingers crossed that I don’t come home to a green pool. Here are my numbers:

Last night at sunset:
FC 12.0
CC 0.4

This morning before sun hit the pool:
FC 11.5
CC 0.5

The CC is right at 0.5 which worries me a little.

Do you think I’m not done?
 

justinc

Gold Supporter
Apr 3, 2019
591
Texas
Are you able to still see any algae? How is the algae problem?

What are your other results? pH, total alkalinity, cyanuric acid?
 
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Donldson

TFP Expert
LifeTime Supporter
Jun 12, 2009
4,696
NW Ohio
If the algae only comes around when the chlorine drops or the temperature jumps too high then it sounds like normal algae and not mustard. Which is a good thing, mind you.

SLAM Process is much different than the nuke and pray technique it appears you have been doing, it is a process that is much safer for the pool and works to eradicate everything living in the water. Following it exactly is the key, too many people try playing with the idea, adding more chlorine, using other products, looking for shortcuts, etc. Also if your CYA is 50 and you are soon to be leaving for an extended time with pucks in the chlorinator you are going to want to bring that down before starting the SLAM. It's going to go back up while you are gone and you would have to do it then if not now, so might as well do it now and not have to bring your FC up so high to SLAM.

One last thing: do you still have the bottle of Yellow Out and can share the active ingredient? There's several brands that use that name and some of them are relatively harmless, but some will mess up your chemistry for a long time.
 

CrisH

Member
Jun 1, 2019
5
Marietta, Georgia
Are you able to still see any algae? How is the algae problem?

What are your other results? pH, total alkalinity, cyanuric acid?

It’s clear and looks great. But it was clear when I saw the algae on Monday. That’s when I shocked it and brought it up to 29 FC with bleach. I don’t have the complete Taylor lot so I’ll have to take a sample to the pool store this afternoon. I know, I have to buy the kit. Last I checked CYA was 50, PH 7.7, TA 80
 

CrisH

Member
Jun 1, 2019
5
Marietta, Georgia
If the algae only comes around when the chlorine drops or the temperature jumps too high then it sounds like normal algae and not mustard. Which is a good thing, mind you.

SLAM Process is much different than the nuke and pray technique it appears you have been doing, it is a process that is much safer for the pool and works to eradicate everything living in the water. Following it exactly is the key, too many people try playing with the idea, adding more chlorine, using other products, looking for shortcuts, etc. Also if your CYA is 50 and you are soon to be leaving for an extended time with pucks in the chlorinator you are going to want to bring that down before starting the SLAM. It's going to go back up while you are gone and you would have to do it then if not now, so might as well do it now and not have to bring your FC up so high to SLAM.

One last thing: do you still have the bottle of Yellow Out and can share the active ingredient? There's several brands that use that name and some of them are relatively harmless, but some will mess up your chemistry for a long time.

Thank you. The YO is from Leslie’s
 

Donldson

TFP Expert
LifeTime Supporter
Jun 12, 2009
4,696
NW Ohio
Ah good, that should just be the ammonia based version. Doesn't really help all that much, we definitely don't recommend using it, but it doesn't do anything to mess up the water chemistry long term.

Pool store water testing is notoriously unreliable, I wouldn't bother taking a sample in because we won't offer any advice based on it. That's why we are so bullheaded about being able to do your own testing, we trust a complete novice doing their first test more than any pool store employee.
 
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