Why Pool Algae Keeps Coming Back (And How to Finally Stop It)
Darren moved into his new home in Rocklin excited to finally have his own pool. He shocked it, skimmed it, and even bought the fancy robot cleaner. But two weeks later, the water turned green. So he cleaned it again. And again. By the end of summer, Darren was spending more time battling pool algae than actually swimming.
If you’ve dealt with algae that just won’t quit, you’re not alone. Plenty of pool owners around Lincoln, Loomis, and Granite Bay are stuck in the same loop: treat, clear, wait... green again.
Let’s talk about why pool algae keeps coming back—and how to stop it for good.
The Truth About Algae in Swimming Pools
Algae isn’t just a visual problem—it’s a sign that your water chemistry, circulation, or cleaning routine is off. Algae can sneak in through rain, wind, leaves, or even a swim suit that just came back from the lake.
If the conditions in your pool are just right, that tiny bit of algae can grow fast. And if you don’t eliminate the root cause, it’s going to come back again and again.
Common Reasons Algae Keeps Returning
Before you can stop the cycle, you have to understand what’s behind it. Here are the most common causes of recurring algae problems in Northern California pools:
Poor Water Balance
If your chlorine levels, pH, or alkalinity are out of whack, your sanitizer won’t work properly. That opens the door for algae to grow—even if you're adding chlorine.
Water balance isn’t just about hitting a number. It's about keeping those numbers stable over time. Sudden drops or spikes can lead to algae blooms overnight.
Weak or Inconsistent Circulation
Your pool filter and pump should keep water moving through the system several hours a day. If your pump isn't running long enough—or your water flow is weak—dead spots form. Algae loves still water.
Check areas like behind ladders, corners, and steps. These places often get ignored and are perfect hiding spots for early-stage algae.
Dirty or Overloaded Filters
Even if your chemical levels look right, clean filters are a must. A clogged or worn-out filter can’t trap microscopic algae spores. Over time, those spores build up—and then bloom.
If you haven’t cleaned your filter on a regular basis, or it hasn’t been replaced in a while, algae will find a way back.
Not Shocking Enough (or the Wrong Way)
A quick shock treatment can help—but if you underdose, you might just stun the algae instead of killing it. That gives it time to bounce back.
Also, shocking during the heat of the day can reduce effectiveness. And if your water temperature is high, you may need a stronger dose to break through the biofilm algae uses for protection.
Algae Types Require Different Treatment
Some algae are tougher than others. Green algae is common and easy to spot. But yellow or mustard algae clings to walls and resists standard treatments. Black algae digs into plaster and needs brushing to remove.
Using the wrong chemicals or skipping brushing allows some types to survive even after water looks clear.
How to Break the Algae Cycle for Good
Ready to stop wasting money on shock and frustration? Here’s what works—really.
Step 1: Get Your Chemical Levels Checked
Take water samples to a professional or use a high-quality test kit to check:
Chlorine and bromine levels
pH and alkalinity
Calcium hardness
Cyanuric acid (stabilizer)
Keeping a proper sanitizer level and balanced water chemistry helps prevent algae from gaining a foothold.
Step 2: Deep Clean the Pool
Brush all surfaces—including the walls, steps, and floor—to remove algae spores. Pay extra attention to tile lines and shaded areas. Vacuum the debris out or backwash the filter.
Use a pool-specific cleaning solution to scrub areas algae may cling to.
Step 3: Shock Like You Mean It
Use a strong shock treatment after sunset when the sun won’t burn it off. For recurring issues, a multi-day shocking plan might be needed, especially with stubborn mustard or black algae.
Don’t forget to run your pump continuously for 24 hours during this process to keep water flow steady.
Step 4: Clean or Replace the Filter
After shocking, always clean your filter—or better yet, use filter cleaner to remove trapped spores. If your filter is worn or doesn’t seem to do the job, replacing it can help restore water quality and prevent future blooms.
Step 5: Stay on a Regular Maintenance Plan
This includes:
Testing chemical levels weekly
Cleaning baskets and skimmers
Monitoring water balance
Running the pump daily during the warm season
You can’t fix algae with a one-time treatment. You need a regular maintenance routine to keep it away for good.
The Cost of Doing Nothing
Ignoring recurring algae doesn’t just lead to green water. It can cause:
Cloudy water that looks uninviting
Foamy water from chemical imbalance
Damage to hot tub surfaces or plaster
Poor water quality that irritates skin and eyes
Long-term buildup that results in costly repairs
It also takes a toll on your pool equipment, requiring earlier replacement of pumps, filters, and heaters due to overload and wear.
American Dream Solves Stubborn Algae Problems
If algae keeps coming back, it might be time to call in professionals who understand local pools—and the water challenges that come with them. At American Dream Pool & Spa Service, we help homeowners from Lincoln to Penryn eliminate algae problems for good.
We offer maintenance services, algae treatment, filter cleaning, water balancing, and seasonal support across Rocklin, Roseville, Granite Bay, Loomis, and more.
Don't let algae take over your summer. Get your swimming pool back—and keep it that way.
