Mustard Algae on pool walls

[Kayakersmith]

Hi,

Last night I found patches of light yellow something in 10-12 different spots on my (30,000 gallon) gunite pool walls. Aggressive brushing removed some, but not all, of the yellow. A little research (thanks Pool Forum!) leads me to believe that I'm seeing an early breakout of mustard algae.

The water is crystal clear, although since the kids have lost interest in swimming over the last few of weeks I've been less than diligent in testing the chlorine levels (I've been testing every 5-7 days and finding FC levels near 0 then adding 4 gallons of 8.25% bleach). The pool has been (and is) crystal clear the whole summer.

Readings from last night using my Taylor 2006 Kit:

FC after adding 4 gallons 8.25%- 7 ppm; pH- 8+ with acid demand of 3 drops; TA- 100; Calcium-250; CYA-100

The suggested Mustard Algae Shock Level from the Pool Calculator is 54. I added roughly 3" of water (22 x 40 x 4.5 pool) in an attempt to bring down the CYA and therefore the required FC shock level. Last night I added another 8 gallons of 8.25% (on top of the initial 4).

This morning the FC level was 26 and the CYA was 85-90. There are still some light yellow patches that do not respond to brushing. With the reduced CYA the mustard algae shock level is now 47.

So my question is, given the relatively small amount of algae present and the visual condition of the water, do I really need to raise and maintain the chlorine levels at 47 until the yellow patches are gone? Or will raising and maintaining some lower level nip this in the bud? We will probably close the pool at the end of September (we're located in Maryland) so I'd rather not spend a lot of time/money fighting this so late in our season. Also, if I do need to raise the FC to 47 could Cal-Hypo (or some other chlorine source) be used to raise the level? I typically use liquid chlorine but really don't feel like dealing with 20+ gallons of bleach

Thank very much in advance for any help,
Mike

[CarlD]

Are you brushing the pool walls? Need to knock the algae off.