Thin green algea problem.

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I

ianwelch001

Active member
May 9, 2024
29
Rochester, NY
Pool Size
35000
Surface
Vinyl
Chlorine
Liquid Chlorine
Hey guys,
Not so new to pools but have had an issue the past 2 weeks and can't figure it out
Every day I have to sweep the bottom of the pool to get a thin layer of algea up. I've never had this problem before and I've certainly never had to sweep it every day.

35k gallon chlorine pool
No solar cover on it
Nautilus CC runs everyday
Liquid chlorine only

Here's my numbers using a tf-100 kit
Ph: 7.4
FC: 7
CC: 0
TC: 7
CYA: 50
ALK: 90
CAL: 220

I just finished a SLAM recently keeping my chlorine around 20
Backwash 2 times a week.
Not sure what else to do.
When I backwash, I can see the algea running out the backwash hose so I know it's being removed.
I don't use algecides or clarifiers just chlorine and acid when the PH rises

Here's a couple pictures

Please help me. I can always see a slight tinge of green in the pool and I'm OCD
 

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To confirm: you passed an OCLT and this wasn't showing up when you brushed at the end of the SLAM Process? It didn't happen until after you let your FC drop?

The look is a bit concerning (very good pictures, BTW, the poof of stuff is visible and useful to helping diagnose it), but I want to rule out a few things before we even consider the dreaded "M" word.
 
Donldson said:
To confirm: you passed an OCLT and this wasn't showing up when you brushed at the end of the SLAM Process? It didn't happen until after you let your FC drop?

The look is a bit concerning (very good pictures, BTW, the poof of stuff is visible and useful to helping diagnose it), but I want to rule out a few things before we even consider the dreaded "M" word.
Click to expand...
Yeah 0 Chlorine loss overnight.
Not sure about the brushing because I didn't think I'd need to right after a SLAM but that was 3 days ago and I've had to brush the last 2 days to get it up.
I have a sand filter and the sand is 4 years old, Any chance it could be shooting it back into the pool because of the old sand not being able to completely filter it?
 
Typically means you need to brush more. Algae can create a very efficient barrier. Brushing, etc disrupts that barrier so the chlorine can work.
 
Sand is millions of years old, a few years in your filter doesn't amount to a drop in the bucket. Filters aren't designed to filter out live algae anyway.

Were you brushing during the SLAM Process? Algae that sits on surfaces forms layers where only the outside layer dies and the inside layers continue to thrive. So the pool surfaces need to be brushed and exposed to the chlorinated water. And if you don't know if this was happening during the process or not then you can't be confident you passed the "no visible algae" criteria. So it's likely you just called it complete a bit prematurely. It happens, just have to jump back in and make sure to get it all.

Now, if you complete the process, nothing poofs when the FC is elevated, and upon returning to target levels this starts happening again, then we have further steps that might be necessary. But no sense getting ahead of ourselves when the easiest answer is also the most likely.
 
+1. You shouldn't even waste your time on OCLTs until there are zero traces of algae, including poofing. :)
 

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I've been dealing with an algae problem for a while now. Everyday I go out and have to brush the pool and poofs of green come up. My numbers are

PH: 7.8
FC: 8
CC: 0
CYA: 60
ALK: 90
CH: 200

I've done about 5 SLAMS the last month or so and have been checking my overnight chlorine loss and every day it is 0.
I've gone through so much liquid chlorine, I should have just kept my boat. It was cheaper to maintain.
My PH is slightly high but that's because of how much chlorine I've been adding to SLAM it all those times.

My chlorine stays between 7 and 10ppm

I swept my pool yesterday and went out tonight and noticed a slight tinge of green on the white stairs so I swept the whole pool again and the algae would poof when the broom went across it.
I've also been keeping my single speed pump going 24/7 and my robot cleans once a day
I'm just not sure what to do anymore.
I'm in NY and the temps have been in the 50s at night and only 70 during the day so it's not super hot

Please help
 
For a CYA of 60 your SLAM chlorine level is 24 ppm. Use PoolMath to figure out how many gallons of liquid chlorine that is and then get it into the pool. Are you maintaining the SLAM level throughout the days of your SLAM or only when you have time? If not daily then your SLAM can take forever. You say you have done 5 SLAMs in the last month but that is not how this works. The SLAM begins and continues until you meet the three criteria for the ending. That can take days or weeks depending on how difficult it is to rid the pool of the algae and how fastidious you are at keeping the FC level up and brushing the pool regularly.
 
TinFoilHat said:
For a CYA of 60 your SLAM chlorine level is 24 ppm. Use PoolMath to figure out how many gallons of liquid chlorine that is and then get it into the pool. Are you maintaining the SLAM level throughout the days of your SLAM or only when you have time? If not daily then your SLAM can take forever. You say you have done 5 SLAMs in the last month but that is not how this works. The SLAM begins and continues until you meet the three criteria for the ending. That can take days or weeks depending on how difficult it is to rid the pool of the algae and how fastidious you are at keeping the FC level up and brushing the pool regularly.
Click to expand...
Yes i was keeping it between 20 and 25 adding chlorine 3 times a day to do so. I say 5 times in a month but it's more like a month and a half.
I would meet all 3 criteria then a few days later I would sweep and see algae so i would start the process all over.
Here's a Pic of the algae i would see just days after a SLAM and with my chlorine consistantly between 7 and 10ppm
 

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You have something that is hiding.
Scrub everything.
The strip around the pool steps holding the liner.
The skimmer face plates.
Remove any main drain covers, scrub them and in the drains.
Skimmer pots.
Skimmer weir doors.
Remove the ladder and scrub INSIDE and outside the ladder.
1726017834692.png

Ask me how I know.
3.jpg

3.jpg

 
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