I think I've got mustard algae?

[zonkakiick]

I see some discoloration on the walls of the pool (yellowish, I would say and it seems to be more on the shaded side of the pool). I've tried to brush to moderate effect. I've shocked to chlorine to16 and checked overnight and it is still 16 the next morning and CC is 0. I brushed it for a week, keeping the chlorine at 16 for 4 or 5 straight days, but I don't know what I'm accomplishing as I'm barely losing 1 chlorine for an entire day (and, again, it doesn't change over night). I thought I might have had it beat, but I think I'm seeing it again a week later. I'm stumped. I'm reading online that I have to vacuum? I've never done that and don't own one. I live in Phoenix area and the pool is a little over a year old. I'm pretty good about keeping my FC at 5, or higher (maybe have let it slip into the 4 on rare occasion). My CYA is 50, so I'm not sure how this ever happened.
Thanks for any ideas

 

[proavia]

Post a full set of current test results from one of the recommended test kits.
Test Kits Compared

FC
CC
pH
TA
CH
CYA
Water temperature

Do an Overnight Chlorine Loss Test
If you fail the OCLT, SLAM Process
If you really have mustard algae, follow the mustard algae protocol - AFTER you successfully complete all three criteria of the SLAM.

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[zonkakiick]

I see some discoloration on the walls of the pool (yellowish, I would say and it seems to be more on the shaded side of the pool). I've tried to brush to moderate effect. I've shocked to chlorine to16 and checked overnight and it is still 16 the next morning and CC is 0. I brushed it for a week, keeping the chlorine at 16 for 4 or 5 straight days, but I don't know what I'm accomplishing as I'm barely losing 1 chlorine for an entire day (and, again, it doesn't change over night). I thought I might have had it beat, but I think I'm seeing it again a week later. I'm stumped. I'm reading online that I have to vacuum? I've never done that and don't own one. I live in Phoenix area and the pool is a little over a year old. I'm pretty good about keeping my FC at 5, or higher (maybe have let it slip into the 4 on rare occasion). My CYA is 50, so I'm not sure how this ever happened.
Thanks for any ideas

FC 16
CC 0
pH 7.6
TA 70
CH 480
CYA 50
I did OCLT and it didn't change and no CC.
Can mustard algae be present if I passed OCLT?

 

[Newdude]

Can mustard algae be present if I passed OCLT?

Yes. In fact, the MA protocol is to pass a SLAM first, including the OCLT, before raising the FC to 60% of your CYA for 24 hours.