Mustard Algae SLAM

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S

Steingreaber

Member
Jul 28, 2020
8
Albuquerque, NM
Pool Size
23000
Surface
Plaster
Chlorine
Liquid Chlorine
We've had a mustard algae problem for a long time now. Started SLAM process 6 days ago. Current chemistry is:
PH 7.3
CYA 34
Alkalinity 88
CH 245
Maintaining FC of 21 (or a bit higher) as calculated with CYA at 34. The water looks clear and algae is barely present when brushing. However, we continue to lose 2.5 to 4 ppm of FC each night. Any suggestions? Should we just continue SLAMing? Is is helpful or advisable to add algaecide (Silvertrine or something similar) while SLAMing? Thanks for any and all help!
 
Algaecide would only be a waste as the chlorine will eat it up. During the standard SLAM Process, there is no need to go above the designated SLAM level for your CYA as the chlorine will just be wasted to the sun. If we round-up your CYA to 40, then an FC of 16 is adequate enough. But losing 2-4 ppm of FC each night means something is eating that chlorine. Some things to be mindful of:
- Pump should be on 24 hrs to circulate chlorinated water.
- Take water samples from the same location of the pool
- If you have a large pool light, remove it (power OFF) and place it on the decking to clean the niche
- Any hollow steps or ladders in the pool?
- Main drain? Check under the cover for algae
- Brush daily and vacuum if junk settles to the bottom; backwash when pressure increases by 25%
- Now if your CYA test is off (too low) then your FC level will also be low; so be sure about the CYA

If there are any unique features to your pool, post a pic to let us know. Chlorine at the proper level is your best defense.
 
Thank you for your reply and tips. TFP pool math calculator indicated we need 21 ppm FC for mustard algae shock. I certainly don't want to overuse. Can you explain how you got to 16 ppm? Did I make a mistake using the pool math calculator?

in response to your tips: Pump is running 24/7. Have not removed pool light and have not checked main drain for algae, but I suspect there may be an issue there. We've had mustard algae issues for the past 3 summers. Never had a problem the previous 9 summers living here. Last year, CYA was off the charts (~120), so we drained all the water out of the pool in April 2021. We also scrubbed the entire plaster surface with water / bleach mixture and added fresh water. In addition, we upgraded from old single speed pump to Pentair variable speed pump and changed chlorinator to non stabilizer (NST) system. Also added Zodiac Nature2 Express cartridge. With all of this, we thought we'd solve the mustard algae problem for sure.

We opened the pool in early May. When we turned the pump on, a bunch of sludgy brown stuff came up out of the main drain. I didn't know what to think about it at the time. It disappeared with pump running and chlorine added. Thinking back now, could that have been algae that was trapped in the PVC below? Within a few weeks of opening, our mustard algae was back and we've been battling it again all summer.

Again, your information and advice are much appreciated! Thanks, Kirk
 
Steingreaber said:
Thank you for your reply and tips. TFP pool math calculator indicated we need 21 ppm FC for mustard algae shock. I certainly don't want to overuse. Can you explain how you got to 16 ppm? Did I make a mistake using the pool math calculator?

in response to your tips: Pump is running 24/7. Have not removed pool light and have not checked main drain for algae, but I suspect there may be an issue there. We've had mustard algae issues for the past 3 summers. Never had a problem the previous 9 summers living here. Last year, CYA was off the charts (~120), so we drained all the water out of the pool in April 2021. We also scrubbed the entire plaster surface with water / bleach mixture and added fresh water. In addition, we upgraded from old single speed pump to Pentair variable speed pump and changed chlorinator to non stabilizer (NST) system. Also added Zodiac Nature2 Express cartridge. With all of this, we thought we'd solve the mustard algae problem for sure.

We opened the pool in early May. When we turned the pump on, a bunch of sludgy brown stuff came up out of the main drain. I didn't know what to think about it at the time. It disappeared with pump running and chlorine added. Thinking back now, could that have been algae that was trapped in the PVC below? Within a few weeks of opening, our mustard algae was back and we've been battling it again all summer.

Again, your information and advice are much appreciated! Thanks, Kirk
Click to expand...
Just wondering if you ever solved your problem. We've been dealing with it all summer and I'm at a loss.
 
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