Battling mustard algae

Sarah12345

Member
May 27, 2021
11
Illinois
Pool Size
16000
Surface
Vinyl
Chlorine
Liquid Chlorine
Hello! New to pool care & had some small piles of stuff on the bottom of the pool that proofed up when swept. I believe it is mustard algae.
~16000 gal, CYA=60 (really close to 50 but not quite visible enough to call it 50), TA=130, pH=7.0, I started a SLAM two nights ago.
5/25, 10:30pm FC= 39.5
5/26, 7am FC= 36 (CC=0.5). Added 50 oz. sodium hypochlorite. Vacuumed to waste & cleaned filter.
5/26, 12:30pm FC= 32 (CC=0.5) It was 85 degrees & full sun. Added 36 oz. sodium hypochlorite
5/26, 4pm, didn't check FC but put in 48 oz sodium hypochlorite
5/26, 8:30pm FC= 32 added 134 oz sodium hypochlorite
5/26, 10pm FC= 40
5/27, 7am FC= 37.5. Vacuumed to waste and cleaned filter.
I also have a Nature 2 cartridge- not sure if that is relevant.
It seemed like less stuff today. But still see piles. Pump on high 24/7.
Should I just keep going with this? I want to finish the SLAM but need advice if I'm on the right track. Thank you!
 

Sarah12345

Member
May 27, 2021
11
Illinois
Pool Size
16000
Surface
Vinyl
Chlorine
Liquid Chlorine
Welcome to the forum!
Please read Mustard Algae - Trouble Free Pool
You need to complete a full SLAM Process and THEN go to Mustard Algae FC levels for just 24 hours.

I suggest you read ABC's of Pool Water Chemistry.
Since I am at mustard algae FC levels already, can I just continue like this? Understand it was maybe more expensive and harder on the equipment? Or would you suggest I let the FC drop back down and do the SLAM. Then when that is done go to mustard algae FC level again? Thanks
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
42,043
Laughlin, NV
Pool Size
6000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
You have not completed your signature so I do not know what your pool surface is, equipment, etc. If vinyl, what you are doing will not be good if kept up for the duration of the SLAM Process

Once you complete the three criteria for a successful SLAM, you raise the FC and maintain at Mustard Algae levels for 24 hours. Then you maintain your FC at elevated maintenance levels for mustard algae for several weeks.
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
42,043
Laughlin, NV
Pool Size
6000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
 

Sarah12345

Member
May 27, 2021
11
Illinois
Pool Size
16000
Surface
Vinyl
Chlorine
Liquid Chlorine
You have not completed your signature so I do not know what your pool surface is, equipment, etc. If vinyl, what you are doing will not be good if kept up for the duration of the SLAM Process

Once you complete the three criteria for a successful SLAM, you raise the FC and maintain at Mustard Algae levels for 24 hours. Then you maintain your FC at elevated maintenance levels for mustard algae for several weeks.
Updated the signature - it is vinyl. When I drop the FC to 40% of CYA, it seems like the stuff comes back and doesn't decrease daily. At FC =40% of CYA even when the FC level stays within 1 ppm overnight, there is still stuff in the bottom of the pool. To pass the SLAM, it has to hold FC overnight within 1ppm, CC less than 0.5, and water clear. Does that mean no stuff at the bottom or just clear water? Thanks again very much for the info.
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
42,043
Laughlin, NV
Pool Size
6000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
Updated the signature
You need to fill out the signature block in your Profile. See our signatures for examples. If on a phone, turn the phone sideways to see our signatures.
To pass the SLAM, it has to hold FC overnight within 1ppm, CC less than 0.5, and water clear. Does that mean no stuff at the bottom or just clear water?
The first sign the process is complete is crystal clear water. That means no stuff on the bottom of the pool.
When I drop the FC to 40% of CYA, it seems like the stuff comes back and doesn't decrease daily.
That implies the CYA value may not be correct. How are you testing your water chemistry?
 

Sarah12345

Member
May 27, 2021
11
Illinois
Pool Size
16000
Surface
Vinyl
Chlorine
Liquid Chlorine
You need to fill out the signature block in your Profile. See our signatures for examples. If on a phone, turn the phone sideways to see our signatures.

The first sign the process is complete is crystal clear water. That means no stuff on the bottom of the pool.

That implies the CYA value may not be correct. How are you testing your water chemistry?
For CYA I'm using Taylor R-0013 reagent and the cylinder with the black dot I got in an HTH 6 way test kit. Watched a video on how to check CYA on sunny day with back turned and look for dot at a glance with cylinder waist level. At 60 the dot is clearly present. At 50, it's faint enough that I don't think it qualifies, so I'm using 60 for my calculations.
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
42,043
Laughlin, NV
Pool Size
6000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
OK -- so CYA should be good.
That kit cannot test the levels of FC you are reporting. How are you testing the FC?
 

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mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
42,043
Laughlin, NV
Pool Size
6000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
Taylor FAS-DPD chlorine test
Great. Would be very helpful to add what test kits you use to your signature. See ours for examples.

I would stay with the normal SLAM Process. If you are not concerned with fading your liner, then do what you are doing.
 

Sarah12345

Member
May 27, 2021
11
Illinois
Pool Size
16000
Surface
Vinyl
Chlorine
Liquid Chlorine
Great. Would be very helpful to add what test kits you use to your signature. See ours for examples.

I would stay with the normal SLAM Process. If you are not concerned with fading your liner, then do what you are doing.
Ok, I will add test kit info to my signature. Thanks again. I'm not worried about fading, just want to get rid of this annoying stuff!
 

Sarah12345

Member
May 27, 2021
11
Illinois
Pool Size
16000
Surface
Vinyl
Chlorine
Liquid Chlorine
Ok, I will add test kit info to my signature. Thanks again. I'm not worried about fading, just want to get rid of this annoying stuff!
This morning there was a 3ppm FC drop from last night. Vacuumed to waste and cleaned filter. Seems like less of the stuff maybe. It stormed last night so there were leaves and other debris too so it was a little tricky to tell what was what. Since still not passing the OCLT, will keep going another day.
 
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Sarah12345

Member
May 27, 2021
11
Illinois
Pool Size
16000
Surface
Vinyl
Chlorine
Liquid Chlorine
Last night was a 0.5ppm FC drop. CC was 1 ppm and still see a few fainter spots. Still keeping the chlorine high another day, vacuuming to waste and brushing 2-3 times a day. Today is better than before but also temps dropped to the 60s so maybe that is helping.
 
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Webster

Gold Supporter
Jun 6, 2021
20
Nashville
Pool Size
29600
Surface
Vinyl
Chlorine
Salt Water Generator
SWG Type
Hayward Aqua Rite Pro (T-15)
Last night was a 0.5ppm FC drop. CC was 1 ppm and still see a few fainter spots. Still keeping the chlorine high another day, vacuuming to waste and brushing 2-3 times a day. Today is better than before but also temps dropped to the 60s so maybe that is helping.
Hi Sarah. As I am in the middle of this same process I'm curious to hear how it turned out?
 
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Sarah12345

Member
May 27, 2021
11
Illinois
Pool Size
16000
Surface
Vinyl
Chlorine
Liquid Chlorine
Hi Sarah. As I am in the middle of this same process I'm curious to hear how it turned out?
Hello! Well, I did finally fix the issue I was having, but I also realized that what I was seeing was possibly just debris collecting in the small dips in the bottom of the pool. It was a yellowish color and "poofed" when disturbed, so I thought it was mustard algae. Now, I'm not so sure. I ended up slamming and vacuuming to waste over & over and it gradually went away. The reason I think it may have just been debris is that I see smaller amounts now just after rain. Hope this helps.
 

Webster

Gold Supporter
Jun 6, 2021
20
Nashville
Pool Size
29600
Surface
Vinyl
Chlorine
Salt Water Generator
SWG Type
Hayward Aqua Rite Pro (T-15)
Hello! Well, I did finally fix the issue I was having, but I also realized that what I was seeing was possibly just debris collecting in the small dips in the bottom of the pool. It was a yellowish color and "poofed" when disturbed, so I thought it was mustard algae. Now, I'm not so sure. I ended up slamming and vacuuming to waste over & over and it gradually went away. The reason I think it may have just been debris is that I see smaller amounts now just after rain. Hope this helps.
It does. I realized I have the same problem, although I'm sure I had mustard algae at one point because at the beginning of the slam it all turned grey in color. Since then we see debris in the pool that's the same color which we thought was mustard algae coming back, but it's gritty and grainy in nature and also poofs when disturbed. My CC stays under 0.5 so I wonder if it's an issue with my sand filter kicking bits of sand back into the pool.
 
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Sarah12345

Member
May 27, 2021
11
Illinois
Pool Size
16000
Surface
Vinyl
Chlorine
Liquid Chlorine
Same thing here, the stuff turned grey at one point. I just thought that was due to all the bleach.
Now I see yellowish proofs after rains but I can see it's got tiny leaf bits and pieces that have blown in from trees.
 

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