So I have a SWG pool, CYA is about 60ppm. Last week, I noticed some yellow "dust" in the pool, potentially mustard algae. This was odd as I keep pretty consistent FC levels at or above the mustard minimum. It spread really quickly this past weekend to the point where I'd brush it and it would re-appear only 3-4 hours later.
Naturally, I decided to SLAM. At 60ppm CYA, I shocked up to about 25ppm of chlorine. I passed the overnight loss test that night - no CCs, only 0.5ppm of loss overnight.
The next afternoon, I moved onto the mustard algae shock at about 35ppm. I dumped in all the pool tools plus some inflatable and added 4 gallons of 10% to get up to about 40ppm from ~20. An hour later, ppm was down to about 34 with about 2ppm of CCs. I added 3 more gallons, which should have gotten it up to about 50 ppm. Again, two hours later and I'm back to 34ppm with even more CCs, about 4 ppm! This process continues until over 2 days I've added more than 20 gallons of 10% bleach. FINALLY, I pass the OCLT with no CCs and chlorine stayed at about 38ppm overnight.
Is my thinking correct that this is indicative of mustard algae? No FC loss or CCs at regular shock, but suddenly I'm going through chlorine like there's no tomorrow when I raise above mustard shock level.
Naturally, I decided to SLAM. At 60ppm CYA, I shocked up to about 25ppm of chlorine. I passed the overnight loss test that night - no CCs, only 0.5ppm of loss overnight.
The next afternoon, I moved onto the mustard algae shock at about 35ppm. I dumped in all the pool tools plus some inflatable and added 4 gallons of 10% to get up to about 40ppm from ~20. An hour later, ppm was down to about 34 with about 2ppm of CCs. I added 3 more gallons, which should have gotten it up to about 50 ppm. Again, two hours later and I'm back to 34ppm with even more CCs, about 4 ppm! This process continues until over 2 days I've added more than 20 gallons of 10% bleach. FINALLY, I pass the OCLT with no CCs and chlorine stayed at about 38ppm overnight.
Is my thinking correct that this is indicative of mustard algae? No FC loss or CCs at regular shock, but suddenly I'm going through chlorine like there's no tomorrow when I raise above mustard shock level.
