Ultimate Guide to Pool Algae

While we’re covered algae extensively here at Mr Pool Man but we’ve never done an all-in-one resource that contains everything you’ll ever need to know (and stuff you don’t want to know!) about every pool owner’s mortal enemy: pool algae!

Pool algae is a simple living plant-like organism that lives in water. It’s basically a chlorophyll machine whose purpose in life is simply to transform sunlight and multiply! Yes, we know that’s not a real scientific explanation, but for our purposes as pool owners, that’s the gist of what pool algae is!

As pool owners, we usually classify pool algae not by their type, but by their color. This simplifies things for us so that we’ll know exactly what we’re dealing with. I mean, really, which one is easier to remember? Asking your pool expert about Xanthophyceae or simply saying “I have a mustard algae problem!” Now, let’s look at the different types of pool algae, ranking them from the most common (and easiest to treat) to the more uncommon ones (hardest to treat).

Probably the most common type of algae that pool owners face. This is not one specific type of algae but a group of a few thousand different types of algae that share a common trait, and that’s their color, which is green. Their green coloration means that they have a lot of chlorophyll which gives them the ability to multiply exponentially in no time at all.

Tip: Green Pool Algae is the primary cause of algae blooms and can cause your pool water to green overnight!

Don’t worry too much though, although green pool algae sounds scary, it’s actually the easiest type of algae to control. Keeping your free chlorine levels at the recommended levels of 1ppm to 3ppm is enough to prevent green algae from taking over your pool altogether.

If you already have green algae growing on your pool surfaces, then a good brushing is more than enough to detach them so they can be properly filtered out. Once that’s done, shock your pool and continue to maintain the recommended chlorine levels to ensure that they don’t grow back.

Before we say, “Oh, so green algae isn’t a big deal then” then don’t. Green algae is easy to get rid of if caught and reated early, but green algae is the type of algae that can quickly spiral out of control (even overnight) and can turn your pool from crystal clear into a swampy green mess virtually overnight! And a green pool is something that isn’t easy to deal with. So I guess what we’re trying to say here is that the earlier green algae is treated, the easier the treatment will be, and the more you wait, the difficulty level goes up exponentially!

Unlike green algae that thrives with direct exposure to sunlight, mustard algae can be found in areas of your pool that doesn’t get much sun exposure. Mustard algae can often be mistaken for pollen deposits or sand deposits in your pool since they’re usually in the far corners of your pool and because of their color.

First the good news. Mustard algae isn’t as common as your run-of-the-mill green pool algae. The bad news is that they’re much tougher to get rid of compared to green pool algae. Mustard algae creates the problem of causing your pool to have a high chlorine demand, but the algae in itself is very resistant to chlorine!

Note: Mustard algae can be mistaken for metal staining. If you see the same stains OUTSIDE of your pool then there’s a big chance that the stains INSIDE of your pool is caused by mustard algae.

If you have a confirmed infestation (yes, scary word) of mustard algae, then there are a number of things that you have to do to totally clear your pool of the infestation and to prevent them from coming back.

• The first step is to give your pool a thorough scrubbing with an algae brush to scrape everything off of your pool surfaces, including the algae roots that may have embedded themselves.
• Hook up your vacuum and manually vacuum the scrubbed out mustard algae to waste. Yes, to waste, we don’t want to move the algae from our pool surfaces to our filters, since they’re still alive and we want them OUT of our pool, not just transferred to another location.
• Shock your pool with TRIPLE your usual shocking amount. Since mustard algae is very resistant to chlorine, we will need a LOT of chlorine to effectively kill them. While this is ongoing, keep your pump running for at least 24 hours to ensure that every nook and cranny of your pool is hit with the extra strong chlorine concentration.
• Optional: To be absolutely sure that you’ve gotten every bit of mustard algae, you can do a no-drain acid was to burn off all of the remaining mustard algae from your pool surfaces. Remember, just because they’re not visible, it doesn’t mean that they’re not there.
• After all of that, keep your chemical levels (especially your chlorine/sanitiser) up to the recommended levels, you don’t want to do everything again right?

Black algae isn’t technically black but it’s dark blue/green, but since it comes in very dense clusters (like spots) it will appear as black. Just like with mustard algae, there’s some good news and bad news when it comes to black algae. The good news, black algae is very rare. The bad news? It’s even tougher to remove than mustard algae! So tough in fact that there have been specific chemicals designed exactly just to deal with black algae.

Dealing with black algae in your pool is exactly like dealing with mustard algae, except for the addition of one step which requires the use of a specialized chemical like the Zodiac Black Spot remover

This is a misnomer because there is no such thing as pink algae! Pink algae is actually a type of bacteria which can be introduced to the pool via a number of ways like getting blown in from the wind or maybe someone jumping into the pool without taking a shower. Pink algae (yes, we'll just call it pink algae to avoid confusion) aside from being slippery, is quite harmless in itself so there's nothing to worry about health-wise.

Don’t worry too much though, pink algae can easily be removed just like green algae and it doesn’t take much effort to deal with it. A good brushing and keeping your free chlorine levels at 1ppm - 3ppm is more than enough to rid your pool of pink algae.

And as an added note, pink algae doesn’t “bloom” like green algae so we can rest assured that our pool won’t be turning pink (although it would look cool).

The simple answer? Everywhere! But just to be safe, here are the areas where we have to be extra careful in checking to ensure that we get rid of every bit of algae when we’re cleaning our pools.

• Pool Corners - Easily the most missed part of our pools when it comes to scrubbing. Tight corners allow algae to lie there undisturbed and take root! Corners are also usually missed by automatic pool cleaners so it’s always a good idea to dedicate a few minutes every time we clean our pool to thoroughly scrub out the corners to get rid of every bit of algae.
• Under Ladder Steps - If you don’t see it, it doesn’t mean it’s not there! Another commonly overlooked area of our pool is the space underneath the ladder steps! Although these steps are usually made from stainless steel which prevents algae from taking root, that doesn’t mean that they can’t cling to the surface and multiply from there!
• Inside your skimmer boxes - While not a common place for algae to hide, algae can lurk in your skimmer boxes, remember out of sight, out of mind! So every once in a while, show your skimmer box some love and give it a good scrubbing.
• In your pool water - Even if you can’t see it, your pool water will always have algae, albeit in a microscopic level. (This is where phosphate removers and algaecide come in, to deal with microscopic algae in our pool)

Scared of all of the things you’ve read on how to deal with pool algae? We can actually prevent pool algae from developing, and it doesn’t need any special tools or know-how. All it needs is some dedication and some time on our parts to completely prevent algae infestation in our pools.

• Pool Chemical Balance - I bet you’re already sick of hearing this, but the best thing we can do to prevent algae blooms and green pool water is to make sure that all of the pool chemical levels are at the recommended levels. I mean, they’re recommended for that exact reason, to make sure that your pool water stays crystal-clear all year round.
• Ensure Proper Circulation - Having the proper santisier levels and chemical levels will be useless if that water isn’t being moved around your pool. This step includes keeping your pool pump in shape, your pool filters are clean and filtering your water properly, and of course, running your pump enough on a daily basis that all of your pool water is properly circulated.
• Weekly / bi-weekly shocking of your pool - Even if you’re religious in keeping your pool chemical levels and sanitiser levels up to snuff, it’s always good to give your pool a good shock once a week or once every two weeks to ensure that your pool water is absolutely clean. If you’re having a pool party or have recently seen increased pool usage, shocking the pool afterwards is definitely a good idea since the added bather load will surely have reduced your free chlorine levels significantly.

• Include a thorough scrubbing in your routine - Pool chlorine levels are sometimes not enough to fully prevent algae from taking root in your pool. A good scrubbing is always the best way to scrape any algae that try to take hold on your surfaces. Do this even if there are no visible algae spots or growths. Because once algae is visible, then it might be too late! Of course, it goes without saying that you should use a good quality brush to do your scrubbing!

• Optional: Invest in a robotic pool cleaner - If the previous step (scrubbing routine) sounds like too much work then maybe it’s time to enlist some help by getting a Tornax TX30 robotic pool cleaner to do the scrubbing for you. Not only does it help with preventing algae growth in your pool, but it has a host of other benefits as well!

• Regular dosing with Algaecide - Algaecide is always a good thing to add to your pool. Even if we’re confident in keeping our pool sanitiser levels up to the recommended levels, there will always be times that these levels will drop like during heavy bather loads, rain, extremely hot days (which are the norm here in Australia) and other factors that may cause our chlorine levels to drop and chlorine demand to go up. Algaecide serves as a shield for these times and will prevent algae from taking root. Note: Look for some good quality algaecide like the ones from Zodiac, going for cheap options can more than not cause copper staining in your pool rather than preventing algae stains!

• Testing and removing phosphates from your pool - Another way to prevent algae growth in our pools is to test and remove the source of food for the algae. This is a pretty specialized test as people don’t commonly test for phosphate levels at their pools. We recommend using some phosphate remover after particularly heavy leaf days.

Generally on their own, having pool algae isn’t really a health concern when we see small patches of them around the pool. So unless your kids or your guests have serious health conditions that make them susceptible to infections then it’s perfectly safe to swim with small patches of algae around your pool.

If you already have green pool water then that’s another issue altogether. It’s not the algae that we should be worried about when we’re thinking about swimming in green pool water but in the other things that we may not see in our pool. See, if your chlorine levels aren’t enough to get rid of harmless green algae, then it isn’t enough to kill the other more harmful contaminants like disease-causing bacteria in your pool.

So in a nutshell: Small algae patches = safe to swim in. Green Pool water = it’s a gamble to swim in (probably unsafe). When in doubt, stay out! If it looks too yucky to swim in, then it probably is!

Not only is pool algae an eyesore, but they can cause some permanent damage to your pool’s surfaces. See, your pool surface isn’t perfectly smooth, there will always be microscopic cracks or hairline cracks that lie unnoticed. But once algae get into those cracks and take root, it will expand those cracks and make them more noticeable once the algae get removed.

On top of that, unchecked algae growth can clog your pool filters and will reduce their efficiency, which in turn will reduce their power in filtering out your pool, causing even more algae, causing even more clogging, which is a vicious cycle that just gets worse.

Pool Algae can also take root in your pool’s plumbing, causing clogs and can become a breeding ground for worse things, like bacteria!

While it may sound like a cliche, prevention is always better than cure! Being proactive in our pool care regimen will always go a long way in preventing all of the problems that come with green pool water. I mean, if you think that doing all the scrubbing and chemical balancing while your pool is still crystal-clear is tiring, you should think about all of the scrubbing involved with dealing with green pool water and algae blooms.