It’s easy to see algae when it really takes hold. However, knowing the early signs of swimming pool algae can prevent those ugly spores from growing.
The last thing you want to do is walk out and see your pool turning green, black, brown or anything other than crystal clear water.
Proper maintenance is key. However, early signs of faster growing algae helps you create the right maintenance schedule for your pool and area.
Know The Types Of Algae
It’s not just green algae that appears in your pool. Since each kind can appear in different areas of your pool, it’s important to know the main types.
Green Algae (Chlorophyta)
The most common type. Appears as slimy green growths on steps and corners. Spreads in less than a day but is the easiest to treat with brushing and shock treatment.
Yellow Algae (Phaeophyta)
Also appears brown. Can grow anywhere on your pool surface. Slower growing than green algae but significantly harder to remove. Requires superchlorination or algicide.
Pink Algae
Usually more red or brown than actually pink. Typically shows up around the water line and pipes. The least dangerous type — proper chlorine levels and brushing usually handle it.
Black Algae (Blue Algae)
The worst swimming pool algae. Appears as tiny black spots that won't budge. Embeds into porous pool surfaces and requires a stainless steel brush plus shock treatment to eliminate.
The good news is all of these show very early signs. And, all of them can be removed if you act quickly.
Check Steps And Corners
Green algae is one of the more common types of swimming pool algae and it also appears quickly. In fact, it can spread in less than a day. Keep an eye out for any slimy, green growths on your pool’s steps and in corners. Sometimes, you’ll notice the slimy texture before you really see the color.
If you notice any green algae, clean it using your pool brush. Then, use a shock treatment to sanitize your pool and completely destroy the algae. Using a brush alone won’t remove it from your pool. It just breaks it loose from the pool’s surface.
Brown Or Yellow Spots
Despite being called yellow algae, this type of algae can also appear brown. It appears much like green algae, though it can appear anywhere on your pool. As soon as you notice any of these spots, take action. Yellow algae is slower growing, but it’s harder to get rid of. So, the less it spreads, the better.
Use your pool brush to break the slimy casing around the algae. Without this, it’s harder for the algae to grow and spread. Then, use a superchlorination treatment or algicide to completely remove it.
Watch The Water Line
Pink algae isn’t all that bad. It typically pops up around your pool’s water line. You’ll notice a pink/red/brownish color around the water line. It can also appear around your pipes too. If you notice it, simply brush it away. If you have the proper pool chemistry, your standard chlorine should sanitize it enough.
Tiny Black Spots
Black algae is the most dangerous type of pool algae. It doesn't sit on the surface — it embeds its roots into the porous material of your pool. If left untreated, it can cause permanent staining and structural damage to your pool plaster.
Of all the swimming pool algae, this is the worst. You may not even notice it at first. Since it appears as tiny black spots on the side or bottom of your pool, you might mistake it for dirt. However, this dirt won’t easily move.
If you notice something, use your pool brush to see if it’s dirt/debris or black algae. If it doesn’t budge, you’ll need to use a stainless steel brush to break it loose. This algae doesn’t have a slimy coating. Instead, it spreads into the porous surface of your pool.
You’ll definitely need to use a shock treatment to help kill off any remaining black algae spores.
Preventing Swimming Pool Algae
Early signs of swimming pool algae may mean you need to clean your pool and check your chlorine levels more often. Wind, rain and even swimming elsewhere can introduce algae. It’s a common issue. Regular pool maintenance typically keeps it at bay.
Consistent chlorine in the 2–3 ppm range prevents most algae from taking hold
Removes spores before they can establish. Pay extra attention to corners and steps.
Still water is an algae breeding ground. Proper circulation keeps water moving and chlorine distributed.
Rain and wind introduce organic matter. A post-storm shock kills algae spores before they bloom.
A dirty filter can't catch algae spores effectively. Clean or backwash on a regular schedule.
When pH drifts above 7.8, chlorine loses effectiveness — giving algae an opening to grow
Frequent issues typically mean you need to run your pump more often to keep your water moving. Sunlight plus still water equals an algae breeding ground.
It’s best to clean algae before swimming in your pool. While it’s not always dangerous, it’s healthier to skip a dip in an algae covered pool.
Algae Problems? We Can Help.
Koko Head Pool Service provides professional algae treatment and prevention for pools across East Honolulu. Don't let algae ruin your swim.
Get a Free QuoteNeed help cleaning your pool due to algae or just want to prevent it? Contact Koko Head Pool Service today for a professional clean you can count on.