Algae again… What am I missing?

[Nathan Parker]

Ok, so I thought I killed it last week. Did the shock, brushed like crazy, ran the filter extra long. Water looked good for a bit, but now I’m seeing green creeping back in, mostly near the stairs and in the corners. The test shows chlorine is fine. I’m honestly over it lol. Do I need to deep clean the filter, or am I just not nuking it hard enough? Any help appreciated, this stuff is stubborn.

 

[Ryan Brooks]

Man, I’ve been there. Algae loves corners, steps, and shaded spots where circulation is weak. Even if your chlorine tests okay, the algae can survive in spots where the water doesn’t move well. First thing I’d do is deep clean your filter. If your filter’s clogged with dead algae, it’s just cycling spores back into the water. I’d also hit it with a double shock dose, not just the standard amount. Sometimes the first round weakens the algae but doesn’t kill the roots, especially if it’s been sitting for a while. Brush the heck out of every surface daily for a few days, run the pump non-stop for 48–72 hours, and check your cyanuric acid levels too. If your stabilizer is too high, chlorine loses its punch. Algae’s a pain but consistent pressure clears it.

 

[Olivia Reed]

Dude, same nightmare last month. Cleared it up, thought I was done, then boom, green patches again, like it was hiding out waiting to come back.

So here’s what finally worked for me: checked for phosphates. No idea they were even a thing until someone at the pool store tested and said my levels were through the roof. Algae loves that stuff, and if it’s high, you’ll be fighting it over and over, even if the chlorine looks solid. Used a remover and haven’t seen green since.

Also, this sounds weird, but I started washing my pool brush and vacuum hose with bleach water. If there’s any live algae on your tools and you toss them back in, it can reintroduce spores. Felt like overkill at first, but honestly made a difference.

 

[Jason Bennett]

Ugh, been in the same loop before, looks good for a few days, then green shows up like it never left. What finally clicked for me was realising I’d never actually cleaned behind the skimmer weir or under the ladder steps. Both spots had junk sitting there that never got brushed or circulated properly.

Also, I swapped out my return jet eyeballs for ones with adjustable nozzles so I could get better flow into the dead zones. Sounds minor, but once I aimed the water into those corners, stuff stopped settling as much. I still shock when needed, but fixing how the water moves made a bigger difference than I expected. It might be worth checking those overlooked areas.

 

[Ava Wilson]

I had the same issue a while back. Turned out my filter needed a serious clean—there was a ton of gunk trapped in it. I also started brushing and vacuuming daily for a few days straight, especially around steps and corners. A second round of shock, stronger than usual, finally did the trick. Just gotta stay on it for a bit until it clears up fully.

 

[Mason Blake]

Sounds like you’re hitting all the usual steps, shock, brush, filter, but the green keeps creeping back because algae is sneaky and loves “hidden” spots. A few things people often overlook:

1. Dead zones & poor circulation – Corners, steps, behind ladders, under skimmer weirs, these spots barely get water movement. Even perfect chlorine levels don’t reach the algae roots there. Adjust return jets to push water toward those areas.
2. Filter cleaning – If your filter has gunk or dead algae stuck inside, it just recycles spores. Deep clean or backwash thoroughly before shocking again.
3. Phosphates & nutrients – Algae thrives on phosphates, nitrates, and other nutrients in the water. If your pool has high levels, chlorine struggles. A phosphate remover can help.
4. Tool hygiene – Pool brushes, vacuum hoses, and nets can carry live spores back into the water. Rinse or soak tools in a mild bleach solution.
5. Double shock – Sometimes a single shock weakens algae but doesn’t kill the roots. A “super shock” over two days while running the pump continuously is often what finally breaks it.

Bottom line: it’s less about nuking it harder and more about hitting all the hidden corners, cleaning your system, and cutting nutrients. Once you combine those steps, the algae usually stops coming back.

 

[Ibrahim Mwangi]

I get it, this stuff is exhausting. If your chlorine tests “look fine” but green keeps creeping back on the steps and corners, it is usually one of two things: you have dead spots where water does not move well, or you have a place that is still “holding” algae and reseeding the pool. What I would do is give the filter a real deep clean (proper backwash, or open and rinse if it is cartridge or DE), then focus brushing on the repeat areas including behind the steps, under the ladder, and around the skimmer. After that, aim your return jets so they push water into the corners and steps, and run the pump nonstop for 2 to 3 days to get full circulation. And if you only shocked once last week, sometimes you have to hold chlorine higher for a few days in a row to actually break the cycle, not just make it look clean for a bit.