Why Is My Pool Still Green After Winter?
You walked outside, took one look at your pool, and thought: how? It's been sitting there all winter. Nobody's been in it. It rained a bunch. And somehow, the water is the color of a swamp.
Here's the thing about Pensacola winters: they're not actually winter. Not in the way a pool needs them to be. Up north, pools freeze over, algae can't grow, and owners can genuinely close their pools for six months and come back to something manageable. Down here, we get December afternoons that hit 65 degrees. That's warm enough for algae to stay alive and comfortable while you weren't watching.
So if your pool is green right now, you're not alone. And it's fixable. Let's talk about what's actually going on.
The Short Answer: Algae Won
Green pool water is almost always algae — and algae wins when chlorine loses. All winter, something was slowly draining your pool's ability to fight back: rain diluting your chemistry, leaves and debris loading up phosphates (algae's favorite food), sunlight chewing through whatever chlorine was left, and nobody adding fresh sanitizer to keep up.
By the time February rolls around and the temps start creeping back up, the algae that's been hanging on quietly all winter gets its moment. One warm week and you've got a green pool.
"Pensacola algae doesn't actually take winter off. It just takes it easy for a few months."
What the Gulf Coast Does That's Different
There are a few things about living in Northwest Florida that make this worse than you'd deal with somewhere like Atlanta or Nashville.
First, there's the oak trees. Y'all know about the oak trees. They drop acorns, leaves, and pollen into your pool from roughly October through April — a constant, slow feed of organic material that breaks down into phosphates. Algae eat phosphates. So your oak tree has essentially been catering a meal for whatever's living in your water all winter long. (ACORNS! shakes fist at sky)
Second, our humidity rarely drops low enough to give pools a break. Even in January, the ambient moisture and mild temps mean algae doesn't fully die off — it just slows down. The second the water climbs back into the 60s, you're right back in business. Algae's business.
Third, Pensacola gets real rain in winter. Every time it rains, fresh untreated water is diluting your pool, dropping your cyanuric acid (the stabilizer that protects chlorine from sunlight), knocking your pH off balance, and lowering the chlorine concentration that's already been doing its best with no help.
So What Do You Actually Do About It?
Good news: a green pool after winter is one of the most common things we deal with, and it's very rarely as dramatic as it looks. Here's what needs to happen.
The Fix — In Order
Test the water first. You need to know where your pH, alkalinity, and cyanuric acid are before you throw chemicals at it. Dumping chlorine into water with bad pH is like mopping a floor that's still wet — not very effective.
Balance pH and alkalinity. Get your pH to 7.2–7.6 and alkalinity to 80–120 ppm. These need to be right before a shock will actually work.
Brush every surface. Walls, steps, benches — all of it. This breaks up the algae colonies and exposes them to the chemicals you're about to add.
Shock it — and mean it. For light green water, you need roughly 2–3 lbs of calcium hypochlorite per 10,000 gallons. For dark green or teal-green, you might need double that. Use a pool shock, not just extra tabs.
Run your filter nonstop. 24 hours minimum after shocking. Your filter is what physically removes the dead algae from the water. If you don't run it, the algae just floats around in there like a bad houseguest.
Vacuum to waste. Once the algae is dead (usually turns gray or white), vacuum it out — but set your filter to "waste" so it doesn't cycle back into the pool.
Check for phosphates. If your pool keeps going green even after treating it, phosphates are probably the culprit. A phosphate remover treatment will starve future algae growth before it starts.
When It's Not Just Algae
If you've shocked your pool and it's still not clearing up after 48 hours, or if the water looks teal-blue instead of pea-soup green, there might be a metal issue — usually copper from your heater or equipment — rather than algae. That's a different fix entirely, and adding more chlorine will make it worse.
Similarly, if your water is green but actually clear (you can see the bottom), that's probably a pH issue rather than algae. Chlorine at too high a pH loses almost all its effectiveness. A simple pH adjustment might be all you need.
One thing to skip
Don't add algaecide before balancing your chemistry and shocking. Algaecide is a preventive maintenance tool, not a treatment for an established bloom. It's the pool equivalent of air freshener — it works great to keep things fresh, but it won't fix the actual problem.
How to Make Sure This Doesn't Happen Next Year
The honest truth is that Pensacola pools don't really get to "close." As long as temps stay above 55°F — which here is most of the winter — algae can survive and grow. That means your pool needs some level of attention year-round, even when nobody's swimming.
Keeping your chemistry balanced through winter (even just checking in monthly), maintaining your stabilizer levels, and clearing debris after storms makes a huge difference. It's a lot less work than dealing with a full green pool in March when everyone's suddenly ready to get outside.
If you'd rather just not think about it, that's exactly what we're here for. We keep pools maintained through winter so that when spring hits in Pensacola — which, let's be honest, is basically February — your pool is ready before you are.
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Got questions about your specific situation? Give us a call, shoot us a text, or just reach out through our website. There's no such thing as a dumb pool question, especially when it comes to something as genuinely weird as Gulf Coast water chemistry.
Pool still green? We can fix that.
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