Need some help with yellow/mustard algae

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300winmag

Gold Supporter
Aug 2, 2016
220
Dallas, TX
in ground pool, pebble finish, SWG.

Last weekend I noticed what seemed to be very fine dirt on the sides and bottom of the pool and then tested the water to see that the FC had fallen to only 1. I slammed the pool for 3 days, and then elevated to mustard algae shock level for my CYA (70). However, I then realized that I had not run all my accessories so I activated my open bowl fountains. These collect lots of organic matter, and the initial discharge from them was nasty. This introduction of more bad stuff brought more dusty material to the bottom and sides of the pool, so I have been trying to maintain the algae shock level.

I have disinfected any toys that go into the pool, removed the pool light to blow out its recess, have laundered all bathing suits and washed all towels.

I saw a 10ppm FC drop overnight (with pump running), and the same dusty stuff on the pool bottom & sides this morning, albeit a bit less. The water is definitely clearer, but I can't seem to get rid of the algae. I have been brushing a ton and maintaining my FC. Does the chlorine kill the algae on its own, or does the mechanical action of brushing stir it up and then the chlorine kills it? Does it "die" and then I need to vacuum the dusty debris out or will it fully clear up once its been killed?

Should I just keep at it, or do I need to try something else?

Thanks
 
Sounds like you took one step forward followed by two steps back when you realized not all areas were being treated by the chlorine. So basically you're back to step one of the SLAM Process. That's okay, but be sure to focus on the normal SLAM Process now, then later (if needed), after passing the 3 SLAM criteria. increase to the proper mustard algae level for 24 hrs.

The chlorine kills the live algae, but the mechanical part (i.e. brushing) exposes algae and surfaces that may have a film or protective covering. That's why brushing and sweeping is so important. For now, be sure to maintain the FC level of 28 and inspect, inspect, inspect. If you have a drain, you might consider removing the drain cover(s) to inspect those as well. Good luck!
 
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300winmag said:
s there harm if the FC is above 28 now, or just a waste of chlorine?
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In a plaster pool, mostly just a waste. Of course above SLAM level you also can't be in the water. Best to maintain the proper SLAM FC level and follow the SLAM protocol. It may take a bit of time, but it certainly works. Hang in there. :swim:
 
300winmag said:
When the algae is fully dead, will the “dusty” material that I am brushing be gone, or will I need to somehow remove it from the pool?
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That's were sweeping and vacuuming come into play so that the filter can capture it.

4ppm overnight loss confirms you should maintain the SLAM Process. :goodjob:
 
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300winmag said:
Should i bias my valves to the pool drains vs skimmers (75/25) since most of whats left appears to be on the floor? Or doesnt it matter.

I figure that i can brush it towards the floor drains
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You can try that to see if it works for you.
Go 100% main drain if you'd like to try it. No swimming or anyone in the pool during this exercise though.
 
pH is not valid when FC > 10
Other tests are valid

What was your CYA right before starting the SLAM
I saw CYA 70 above and now today you are reporting CYA 40
If it was 70 on Friday and 40 today, I would look at your testing technique.

During a SLAM, all you test is FC and CC
 
I only retested CYA to confirm where I was at. Seems like something went haywire with the initial measurement, as I retested again and got 40. I am Using the visual cya method in the test kit (k2006)

Assuming 40 is valid and I’ve been running FC of 28 for a week, with a good chunk of one day near 50 for the algae shock, is it possible/feasible to still have organics in the water? CC has been 0.5 or zero for the last two days.

Thanks
 
Was your CYA 70 tested with the same test kit?
You don't test CYA during the SLAM Process

You mention you were at FC 28 and then FC 50 (for a day).
Did you ever fully pass ALL THREE of the SLAM criteria prior to bumping FC to 50 or was the FC 50 something else?
What was the purpose of FC 50?
 
I passed all three. Then when i went to algae shock level i turned on all pumps & accessories and my fountain bowls discharged some nasty stuff, and the next morning the algae was back.
This happened last thu night, so the algae came back fri AM.
 
Gene, I believe the OP is referring to Mustard Algae shock levels, that's why it was higher. "300", are you saying that during the entire SLAM before you never ran the fountains or other plumbing areas? You do want to ensure the elevated chlorine water goes through all of those areas periodically as well in case there is stagnant water or algae in there. You have a main drain(s), so have you ever tried to remove those covers to inspect for algae?

Also, do you have a large light in the pool set into a hollow niche? If you do, you'll want to remove that light (power off) to inspect. If you have the smaller 3.5" LED nicheless lights then don't worry about it.
 
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