Conquering Mustard Algae

[stal1113]

My battle with mustard algae:

10000 gal salt fiberglass pool installed May 2023
pH 7.4
FC 8 ppm
CYA 70
Alkalinity 60
Year 1- FC was a battle to keep above 5 ppm. I routinely added shock and clarifier but what I suspected to be mustard algae always returned. My swg which produces 16 Oz chlorine per 24 hrs had to be turned up to 70 or higher for 12 hrs.

This year, July 2024- Finally decided to perform a SLAM. Results were good as far as water clarity but I was still losing 3 pp. Fc in overnight test. After 5 days I ran out of solution in the FAS-DPD test kit.

Out of desperation, I decided to add algae treatment. After 2 days, the algae was gone, pool crystal clear, overnight test, zero FC lost. I have my swg set at 20% after repeated lowering. My current FC is at 12.0 ppm (purchased more solution). I'm trying to lower it to 8.0 ppm.

I'm sure the SLAM would have produced similar results if I had been able to complete it. I will keep my FC at around 8.0 ppm ongoing according to the cya/fc chart for mustard algae control.

So, for now it looks like a success and hopefully will continue. TFP guidelines really helped.

 

[ajw22]

Welcome to TFP.

What was the algae treatment?

I hope it did not add copper sulfate to your water.

 

[stal1113]

Yes, copper sulfate. I did quite a bit of research and understand (and respect) all of the facts/opinions. I decided to accept the risk, simply to determine if my plummeting FC was due to algae or something else. I do not intend to include future maintenance algaecide doses as I will keep my FC at recommended mustard algae levels and SLAM in lieu of adding algaecide if needed.

Regardless, my SWG is set at 24% (equivalent to 20 Oz 10% liquid chlorine per day) and my FC is still climbing, 12.0 this morning, 13.5 this afternoon. I lowered it to 20% so hopefully that will bring it down. I'm not accustomed to my pool being this clear since it never went a week before getting cloudy from mustard algae. It's now going on 3 weeks.

 

[ajw22]

I wish you luck as copper will stain pools and turn blonde hair green. The only way to get rid of copper in the water is draining the pool which is problematic for fiberglass pools.

Copper in Pool Water - Further Reading

www.troublefreepool.com