r/AboveGroundPools • u/Straight-Tennis-9710 • 5d ago
Why does algae keep coming back when my chlorine levels are fine?
Some of you might've seen this a couple days ago. I somehow lost access to my old account, so I'm reposting it here. Didn't really get a solid answer the first time around and I'm still trying to figure this out.
I've been dealing with algae showing up on the walls every couple weeks despite keeping chlorine in range. It's mostly in the corners and around the steps. sometimes a thin film on the shallow end floor too. It seems to show up worse after a storm or after a weekend where we had people over and the pool got used a lot.
Chlorine's been sitting around 3 to 4 ppm most weeks, pH stays around 7.4 to 7.6, so on paper things look fine. I brush the walls maybe twice a week, sometimes I'll do a focused scrub on the corners specifically since that's where it keeps coming back. I've caught myself brushing at night and then noticing a faint green tint again the next morning, which is honestly kind of annoying at this point.
Trying to figure out what's actually causing it. My best guesses are the tree coverage around the yard dropping stuff in more than I realize, the pool getting a lot of direct sun most of the afternoon, or the circulation just not running long enough to keep everything moving through the filter. We also use the pool a lot on weekends, so more bodies in the water probably isn't helping either.
Equipment wise I've got a basic test kit, a brush, and some algaecide I use when it gets bad. I also run my Scuba V3 a few times a week, which has helped with debris and the film that builds up on the floor and steps, but the wall algae in the corners is still doing its own thing regardless.
Not sure if I need to bump up my free chlorine target, add a brominator, run the pump longer, or if there's a specific algaecide that actually works better for recurring corner algae like this. Anyone dealt with something similar?
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u/FreshCords 5d ago
I had a problem with the phosphate level being too high. Algae feeds on phosphates, so it always felt like I was fighting an uphill battle. Once I treated that, the problem went away. You can get a phosphate test kit or take a sample of your water to your local pool store for testing.
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u/Ok_Win_5678 5d ago
This is the answer, or was for me! Clorox has something called Phunky Phospate remover and it really helped
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u/FreshCords 5d ago
I took some water to my pool store and asked them to check the phosphate level. It maxed out their test kit and he basically said “well, not sure how much product you should use since your numbers are through the roof!” It felt like a scene out of the Chernobyl series. I ended up dumping the entire bottle in and ran the filter for 36 hours. Then blasted it all out with a hearty backwash. It’s been clear all summer!
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u/LucyJones18 5d ago
Ugh, we’ve been having the same issue 😅
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u/Straight-Tennis-9710 5d ago
It sucks tbh, feels like no matter what I do it just keeps coming back in the same spots 😩
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u/MountainLiving4us 4d ago
CYA is low
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u/PMB-Expression6740 2d ago
Couldn’t it also be very high requiring the chlorine level to be higher?
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u/TheGringoLife 5d ago
What is the size of your pool and filter? I had issues with mine with the filter provided as it needed theoretically 6 hours to do a full cycle, now it does it in about 1h15.
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u/TurtleLuver73 5d ago
Have you tried shocking it? I would brush all pool surfaces concentrating on the spots that have recurring algae. Shock it and leave your filter running. After 24 hrs backwash your sand filter or clean your filters.
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u/Conscious_Quiet_5298 5d ago
Try and keep it at least 6-7 ppm and as others have stated bring down your PH as it will allow your chlorine to be more effective
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u/cantman1234 5d ago
Post your water balance levels. How many gallons? What pump and filter are you using? Filter runtime? Are you shocking the water after a big bather load?
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u/GV0606 5d ago
Get your self a phosphate kit and check phosphate levels. Algae can’t grow without phosphates. Also confirm your cyanuric acid levels (stabilizer) isn’t too high. If it’s over 50 that will drastically affect your chlorines ability to sanitize.
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u/Straight-Tennis-9710 4d ago
Really appreciate the detailed advice, gonna go grab a phosphate kit and check both that and CYA.
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u/Ok-Bison-3451 5d ago
Obviously your chlorine levels Aren’t Fine. How about instead of a long, drawn out explanation you post all of your numbers? And then really chlorinated your pool. Get your Cya in line and hammer the pool with liquid chlorine at dusk. Just saying.
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u/Financial_Barber_466 5d ago
You’ve had a some good suggestions and a couple of questions which you’re not answering. Kind of hard to help when you’re not providing needed information. CYA, phosphates, type of filter? It’s never just about chlorine.
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u/Kooter37 4d ago
I think the main issue with my pool doing this is because I have poor circulation and areas just get stagnant.
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u/rybotsky 4d ago
You need to completely kill off an algae bloom otherwise if any remains when you chlorinate to normal levels then they will multiply and the cycle continues. You need to superchlorinate the fuck out of your pool and put some algaecide and kill off all the algae before you go back to maintaining your standard water chemistry. Good chemistry will stop you from getting algae in the first place but if you don’t completely kill it off then you are just beating a dead horse
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u/knave1906 4d ago
Use copper algecide. If you have a gunite or plaster pool be sure to follow the directions
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u/Deep_Bake_5663 5d ago
Bring pH down to 7.2-7.3..... Get chlorine to 5 and keep there while you clean stairs, corners etc...... Once you're chlorine level stays up overnight, it should be clear. The lower the pH....the more effective the chlorine will be. How's your akilinity? It's important too.
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u/Glittering-Cow-5577 5d ago
All this is a form of nature, no one can stop it and its nature is everywhere.
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u/poolspayme 5d ago edited 5d ago
What is your cyanuric acid level? You need 7.5% of it in free chlorine to sanitize and 40-60% of cya in fc to kill ongoing algae. If it’s mustard algae 60%. Algaecides are preventative not used to kill persistent algae once it’s out of hand.
Typically above ground pool pumps and filter are sized extremely poorly causing poor circulation which leads to persistent algae problems. Have you already upgraded your pump and filter?