Am I battling mustard algae or something else

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FoxyRoman

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Nov 1, 2012
18
New Freedom, PA
I've been noticing the accumulation of what I thought was dirt/debris at the junction of my walls, slope and bottom this week. I've had the solar cover on and at first suspected it was somehow making its way into the pool along the edges where there are gaps. FC levels have been steady at 5-5.5. Pulled cover off for kids to swim on Wednesday and brushed the debris (it has a brownish yellow color and poofs up into a cloud when brushed). Was suspicious of algae but was hopiong for the best. Did an OCLT on Wednesday night and had no FC loss on Thursday morning. Got home from work yesterday only to see the dirt/debris had returned. I also noticed some on the steps. There is no pollen on the solar cover or furniture, so I'm assuming I have algae. I SLAMmed last night and brushed everything (including pulling the ladder and popping the light from its niche). Another OCLT check this morning revealed that it held at 24, but with the pool light on I could see that whatever this is was reforming (it was about a 3rd of what it was last night, about 9 hours after I had SLAMmed and brushed). The pool water isn't as sparkling as usual, but I wouldn't call it cloudy either. I can see my main drains and would still be able to tell heads or tails on a quarter in the deep end. In a bit of a panic, I decided to bring my FC up to mustard shock level (35) this morning, rebrushed and now am at work. Here are my SLAM levels:

FC: 24
CC: 0
PH: Was 7.4 before SLAMming
TA: 100
CH: 150
CYA: 60 - 70 (I struggle with this, but I swear I can see hints of the black dot until I reach 60)

I'm really perplexed since I've passed the OCLT 2 nights in a row at different FC levels (5.5 on Wed night and 24 on Thurs night). Does this sound like mustard algae or is it something else? Being in PA, do we even see mustard algae up here (I was always under the impression it was mostly a Sunbelt state problem)? Does mustard algae not consume chlorine?

With realistically only having 2 swim weekends left in the season, should I consider just living with it, let my FC levels drop back to normal, see what happens and fight it (if I have to) when I don't have to worry about an angry wife and kids?
 
What you are seeing is very likely dead algae settling to the bottom. Brush, vacuum and keep your FC at SLAM value and I'll bet it will go away very soon.

Regardless if it is mustard or another of the thousands of types of algae, the cure is the same......SLAM the pool.

Given the condition of your water, filtration is very important at this stage. Clean the filter often, brush often, vacuum when possible, run the pump 24/7 and keep your FC up.
 
FoxyRoman said:
CYA: 60 - 70 (I struggle with this, but I swear I can see hints of the black dot until I reach 60)
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If you can see traces of the black dot until you reach 60, then your CYA is 60. Here is an excerpt from the CYA section of the Extended Test Kit Directions:

Extended Test Kit Directions - Jason Lion said:
Continue pouring until all traces of the black dot at the bottom of the view tube completely disappear, even after you stare at it for several seconds...
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I would suggest doing the CYA test outdoors in the midday sun with your back to the sun while holding the view tube at about waist level.

This page at Taylor Technologies has photographs which show what the view tube looks like when the test is complete: http://www.taylortechnologies.com/ChemistryTopicsCM.ASP?ContentID=44
 
The perplexing thing for me is my FC levels have remained at 4-5ppm for weeks (I'm OCD with my testing). How could it be algae, especially with my OCLTs passing the last 2 nights? Don't misunderstand, I appreciate all the help from this site and your quick response in particular, just confused about what's going on since the telltale warning signs never presented themselves.

One other thing I've noticed is that my sand filter pressure has barely climbed all summer. It starts at 12psi and has barely reached 13psi. I know the gauge works as it increases at higher pump speeds and decreases at lower speeds. It's a new pool, so I can't imagine I've got a sand issue, but what are some telltale signs of a sand filter problem and could that at all be in play here?
 
It just disappears into a poof when I try to. The fact that it reappears in the same locations leads me to believe it's algae, but 2 consecutive nights of passing OCLTs has me really scratching my head. The shallow end water is essentially crystal clear, with the deep end just slightly cloudy as a result of the brushing (the bulk of the substance is in the deepend along the joint where the wall meets the slope and floor).
 
, but 2 consecutive nights of passing OCLTs has me really scratching my head.
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Passing two of the three criteria.....

1. Your pool water is sparkling
2. Your CC's are .5ppm or less
3. You can hold your FC overnight without losing more than 1ppm.

Doesn't mean that the others are a foregone conclusion. Until your water is sparkling with no sign of debris, you should continue to SLAM. Brushing, vacuuming and 24/7 filtration are critical at your point in the progression.
 
Thanks Duraleigh. Makes sense. Last question (I hope/think), is it not out of the ordinary to have something like this happen even without dropping below a min FC-level of 3 for my CYA (I run on average at 5) and immediately passing the OCLT (1 before SLAMming and the other immediately after)?
 
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