Common Types of Algae Found in Swimming Pools and How to Get Rid of Them

Picture this: A beautiful summer day. It’s Saturday. You wake up, make a coffee, have a lovely breakfast, and you go run some errands. During your drive back home the sun is shining on your windshield and all you can think about is jumping straight into your swimming pool to cool off. Then maybe you’ll take out your inflatable mattress and just float around for a couple of hours.

You park, you change into your swimsuit, and do your rendition of the biggest cannonball. The water cools you instantly and you think: “Can today get any better?” And as you run your hand through your hair, you feel something sliding on your shoulder. “But why did this happen? I just cleaned my pool on Monday, how can it have algae?

What causes pool algae?

Just as we have bacteria on our bodies that become a problem in certain conditions so do pools. Algae spores can easily be carried into them by the wind and can grow under certain circumstances.


To prevent said spores from gathering into corners or any other spot on the pool’s surface your pool will need to have a good water flow. Pumps might get damaged or they can malfunction, causing a low or inconsistent flow, a dead spot, or stopping altogether.


Filters are just as important as pumps, and ineffective or cracked filters cause just as much of a problem. And even if they work just fine, the run times can also be an issue.


This refers to the balance of the chemicals in your water. The treatments your water needs should always be performed correctly and timely. Any excess chemical or lacking one can make a world of difference for the balance.


As many say, once a week is the go-to for pool cleaning. Even if everything is working as it should, it doesn’t mean you skip cleaning day. Sediment build-up can also be a lifeline for algae.

How many types are there?

There are quite a few, but for swimming pools, there are four types of algae:

  • Green: if there’s room for algae to bloom, the bloom will likely be of green algae. Floating on its own, gluing itself to the walls, or staining gritty surfaces. Slime galore!
  • Yellow or mustard: having a soft spot for shade and being a frequent resurfacer, this type is hard to get rid of. Check for any floats or toys in the pool before cleaning, seeing as this alga clings to anything and can survive treatment.
  • Pink: Being more so a bacteria than algae, the opposite is required for the pink variety, where you should throw in the pool (during treatment) everything that has been in contact with the contaminated water. Pump up the chlorine level and give everything a thorough brushing.
  • Black: the little black spots are the worst kind of algae you can have the misfortune of encountering. It is tough to remove and has pesky roots that dig deep and cling to everything porous. Once your pool has this type, spend extra attention on treating it. And ask everyone who comes for a swim if they’ve visited the ocean recently, as black algae can stick to bathing suits and use them to carpool.

How to get rid of it?

Unfortunately, algae don’t disappear as quickly as they appear, and it requires a lot of consistent effort to make it go away completely.

If you are one of the lucky ones and there are only one or two isolated blooms in the pool, the answer is chlorine, algae treatment, and elbow grease in the form of brushing.

If your luck has run out, the way to fix it is by checking the same 4 causes. But before doing so you want to thoroughly clean. Skim, brush, and vacuum. Your safest bet would be getting a robotic pool cleaner for this part so that you can focus your energy on the next steps:

  • Balance your chemical levels. Test the water and bring each element in the appropriate range. Shock the pool if the algae blooms are big in numbers.
  • Brush, brush, brush. If you leave the first cleaning to a robot, you now still have the energy to vigorously brush any tough spots that might hang on for dear life. This way you are loosening the algae and making room for the chemicals to do their job.
  • Run your filters. This is the part that turns your weekend from a nice pool break to a “spring cleaning” effort. They need to be on continuously for 18 to 24 hours. Help them by adding a clarifier.
  • After all is said and done, and after your chemicals settle down, you may want to add algaecide. This step is to make extra sure you’re getting rid of your unwanted visitors.

Do not let anyone in the pool during the whole cleaning process to avoid any accidental poisoning.

And then what?

To prevent any more of these unpleasantries keep your eye on every step mentioned. Keeping a good balance isn’t just a one-time thing and proper, constant maintenance is what makes a pool great and swim-ready.

Do your weekly checks and make sure to add if something is lacking. You never know when a little filter malfunction will make its presence (or absence) felt.