Backstory, had pool about five years. Water pretty much managed itself using the advice here and methods. Went a spell early this year without a SWG (replaced it) and went live with it in late spring. During that period we were on pucks and liquid chlorine.
Water has been mostly clear this summer, with a few touches of hazy after big swims. A few weeks ago (or maybe a few months?) I started noticing a significant chlorine drop over the day (like, almost depleted entirely) so bumped the SWG to 100% thinking it was our blazing sun and (unusual) 100 degree temps. Still losing chlorine, and not able to keep at our recommended range even running 24 hours at 100%. CYA is a bit low @ 50 (I like it at 70) but I have hesitated to add more because:
Let's SLAM. This is the third now in about a month, if I remember correctly. Each time, we pass OCLT, including <1ppm loss, no CC, and beautiful sparkly water. Over the course of the next week we seem to drift back into the chlorine demand cycle. We start to lose a ton overnight and SWG can't keep up during the next day.
This weeks SLAM, started on the 7th, with clear water:
Targeting >22 ppm to be safe. We lost 3ppm overnight first evening, I gave it a chlorine hammer (up to 29 ppm) yesterday after sunset, and still lost ~4ppm overnight. We're now clocking in at 12 gallons of 12.5% in two days, just to maintain at 22. CC has varied, usually 0.5 but hits 1 occasionally. I expect to dump at least 4 maybe 6 gallons in today depending on how fast it eats it.
Now, I know green (see my old threads) and this is different. In the past our opening SLAM would keep us sparkly through the year. Maybe a touch up here and there after big swims or storms, but generally no problem. This summer our pool is a chlorine eating monster.
One thing I did notice was a weird yellowish but more brown staining on our steps, and around our first return. Pool is in need of a resurface, so excuse the crappy disintegrating paint job. (And I wonder if all this texture is providing a new home for algae to thrive... ugh.) This area gets afternoon shade.

We've brushed this area out with a stainless algae brush, as well as the steps. And brushed the rest of the pool, too. I plan to pop the light out of the niche this afternoon to see if any uglies are hiding in there. The rest of the pool isn't showing any of the yellow. I can read the words on the main drain cover, through about 9 ft of water.
So - my question. Does this match the pattern of a mustard algae issue? Based on what I read it does, but looking for some confirmation from folks that have faced this challenge.
Tony
Water has been mostly clear this summer, with a few touches of hazy after big swims. A few weeks ago (or maybe a few months?) I started noticing a significant chlorine drop over the day (like, almost depleted entirely) so bumped the SWG to 100% thinking it was our blazing sun and (unusual) 100 degree temps. Still losing chlorine, and not able to keep at our recommended range even running 24 hours at 100%. CYA is a bit low @ 50 (I like it at 70) but I have hesitated to add more because:
Let's SLAM. This is the third now in about a month, if I remember correctly. Each time, we pass OCLT, including <1ppm loss, no CC, and beautiful sparkly water. Over the course of the next week we seem to drift back into the chlorine demand cycle. We start to lose a ton overnight and SWG can't keep up during the next day.
This weeks SLAM, started on the 7th, with clear water:
FC 6.5
CC 0.5
PH 7.8
TA 100
CH 250
CYA 50 (low)
3600 Salt
Targeting >22 ppm to be safe. We lost 3ppm overnight first evening, I gave it a chlorine hammer (up to 29 ppm) yesterday after sunset, and still lost ~4ppm overnight. We're now clocking in at 12 gallons of 12.5% in two days, just to maintain at 22. CC has varied, usually 0.5 but hits 1 occasionally. I expect to dump at least 4 maybe 6 gallons in today depending on how fast it eats it.
Now, I know green (see my old threads) and this is different. In the past our opening SLAM would keep us sparkly through the year. Maybe a touch up here and there after big swims or storms, but generally no problem. This summer our pool is a chlorine eating monster.
One thing I did notice was a weird yellowish but more brown staining on our steps, and around our first return. Pool is in need of a resurface, so excuse the crappy disintegrating paint job. (And I wonder if all this texture is providing a new home for algae to thrive... ugh.) This area gets afternoon shade.

We've brushed this area out with a stainless algae brush, as well as the steps. And brushed the rest of the pool, too. I plan to pop the light out of the niche this afternoon to see if any uglies are hiding in there. The rest of the pool isn't showing any of the yellow. I can read the words on the main drain cover, through about 9 ft of water.
So - my question. Does this match the pattern of a mustard algae issue? Based on what I read it does, but looking for some confirmation from folks that have faced this challenge.
Tony