Does Low pH In The Pool Cause Algae?

A low pH level in a pool comes with a lot of consequences, not only for swimmers but for the pool itself. This is why you shouldn’t let your pool water have a low pH level. It will affect your health and impact your wallet. There’s nothing good about having a low pH level in your pool. But does low pH in the pool cause algae?

Yes, low pH in a pool can cause algae, but not all types of algae. Acidophilic and acidotolerant algae thrive in acidic water. Another way low pH can lead to algae growth is when the acidic water damages the filtration system. Once the filter is damaged, algae and other microbes and contaminants can easily invade the pool.

Having algae in your pool will make your pool very unhealthy, so this post will help you to manage your pool to prevent its occurrence.

Description of pool algae

Pool algae is a group of photosynthetic organisms that usually live in water bodies in a form of green growth. When it appears in your pool you will notice green-tinged water and sometimes it can have telltale dark spots that are always on the wall which indicate a black mold. Algae in pools grow very fast because of the moist, warm air environment.

Does low pH in the pool cause algae?

Yes, as earlier stated low pH level is one of the factors that make algae form in your pool. Once your pool pH level is low, there’s an imbalance that makes your pool water acidic. Acidophilic and acidotolerant algae can thrive in an acidic environment.

So, having low pH in your pool may not attract all forms of algae because not all algae can survive in an acidic environment. But those that are acidotolerant will likely invade the pool.

Moreover, the acidic water in the pool can damage the filter which will create room for algae and other contaminants to enter the pool.

Do pool algae like high or low pH?

According to research, algae generally thrive in high pH, especially between the range of 8.2 and 8.7. But some algae, often referred to as acidophilic and acidotolerant algae, thrive at very low pH. This makes it difficult to control algae with pH variation. So it only with proper chemical balance and a good sanitizing chemical that can prevent it from growing.

Do algae raise the pH level in the pool? Yes, algae can raise the pH in a pool because it feeds CO2. The depletion of CO2 in your pool water can make the pH increase. 

What can increase the growth of algae?

Apart from ph imbalance, other factors can affect algae growth in pool water. The following factors increase the growth of algae:

  • The presence of phosphates – Algae needs phosphate to live and grow. If there is no trace of phosphate in your pool, algae may not be able to grow there.  But with the presence of phosphates in the water algae will be able to bloom faster.
  • Lack of stabilizer in the pool – Cyanuric acid which is a stabilizer prolongs the life of chlorine by slowing the breakdown of chlorine molecules. The sunlight makes the chlorine react faster. So without a stabilizer in the pool chlorine tends to break down a lot faster at elevated temperatures. Once the chlorine sanitizer finishes, the pool is left for infiltration.
  • The improper filtration system of the pool – The fact is that a pool filtration system that isn’t cleaned will trap debris and bacteria. When this happened the filters might be clogged. This will hinder the free flow of water through the filter. This stagnation of water will bring about algae forming unlike when there’s free movement of the water.
  • Incessant pool parties – When there are a lot of people in the pool than necessary the chlorine levels in the pool will dissipate faster. This is caused by swimmers introducing into the pool sunscreen, dirt, and bacteria. The chlorine in the pool will work harder to contend with all these impurities and the chloride level will lower faster. Of course, at that rate, there will be faster algae growth. Low chlorine levels lead to poor sanitation of pools and algae will easily grow in such conditions.
  • Use of plant fertilizer – This is about you using plant fertilizer to keep your facility landscapes green. The two ingredients commonly found in the fertilizer are phosphorous and nitrogen which help the plant to grow better. But at the same time, it can also feed the algae if some of it gets into the pool. This will increase the growth of the algae very fast.

Can you swim in an algae-filled pool?

No, it is not advisable to swim in an algae-infested pool. You should always remember you are only to swim in crystal clear water. Doing otherwise may affect your health. It isn’t that it would be harmful to you especially if it has few patches of algae here and there but it still shows that there are other underlying factors that might be dangerous to your health.

So even when you have your sanitizing chemical chlorine in place and you still noticed algae growth, it shows that your chlorine isn’t effective so as it isn’t killing these algae it means that it isn’t killing other bacteria in the water too. With the presence of microbes in the pool swimmers’ health is at risk. 

How to prevent algae growth

It is always better to prevent a thing from happing by applying its preventive measures than trying to fix it. Fixing things like in this case might come at high risk. So to avoid having health risk and it affecting your pocket, you should always do the following:

  • Have a proper water balance

This is one of the things to do to prevent algae from forming in your pool. Try to have your pH levels in the optimum range which should always be between 7.2 and 7.8. In this case, avoid having a low ph level in your pool. Then other chemical balances like total alkalinity should be 100ppm, calcium level 200ppm, and cyanuric acid at about 30-50ppm. You need to work on your pool chemistry to avoid pool water imbalance.

  • Have a proper filtration system 

You should always be sure that your filtration system is working effectively as it should. Clear it out regularly to remove trapped dirt and debris. When this is clogged, water movement will be restricted and this enables algae not to only form, but to increase rapidly. Always do two turnovers per day. Then you can add a run time that can be between 16-18 hours.

  • Maintain proper circulation

Make sure that your water circulation is consistent. This will create a harsh environment for algae to bloom.

  • Have an excellent sanitation level 

Keep your pool sanitation level very high. You know you should only swim in crystal clear water. So avoid having contaminants in your water. Apply a good measure of chlorine to destroy all bacteria and other organisms. You need to have a consistent daily chlorine dosage of about 2-4ppm. Clean your filter and let it run effectively to help circulate the chemical. Clean your entire pool when the need arises. All of these will help in presenting an unfavorable environment for algae to form or bloom.

  • Use quality algaecide and supplemental sanitizers

You should also be applying algaecide in your pool as a preventive measure, the same way you add other chemicals to your pool during a shock. Try to get a quality one that will serve you better. After using it initially when shocking your pool, you can now be applying it at weekly maintenance doses. You shouldn’t also forget to apply other supplemental sanitizers that can help in preventing algae growth like minerals and having UV or ozone treatment.

  • Use professionals for pool maintenance

You need to be bringing in some experts to help you with your pool care. They are the professionals so they will able to keep your pool free from algae and other detrimental things. You would also be given the best solutions to all your pool problems before it gets worse.

How to fix algae problem in your pool

Well, if you have been unfortunate to have algae already in your pool, you don’t need to panic. There are simple things you can do to remedy the bad situation. Use the following tips to restore your pool to its superstate.

  • Balance your water

You start your treatment with the root cause of the problem which could be low pH. So you start with balancing the water chemistry. So raise your pool pH if the level is low and ensure that your sanitizing chemical is effective.

  • Check that your pump and filter are functional

You need to ascertain that your filter and pump are operating optimally. You can shut down the heater in your pool to help lower the water temperature. Then adjust the valves for excellent circulation, then make the pump run for about 24 hours a day still your pool is clear. You can also turn on the pool cleaners to help in stirring up things and help in backwashing as needed.

  • Clean your pool

You should begin to brush the floors and walls of your pool daily now. Then vacuum any parts that need vacuuming. If your pool is filled with debris and dirt such that you can’t see the bottom of the pool, you need to drain it. You can acid wash it and refill it. But if it is difficult to drain completely, you can take out half of the water and refill that half with fresh water. But try to get almost all the debris off your pool

  • Shock your pool

This is another great thing you might need to do to help your pool. You need to shock it. So apply chlorine and/or non-chlorine shocks that will be helpful to your pool. You can also apply hypochlorite, cyanuric acid, algaecide, and granular pool shock. So use the recommended dozes for your pool.

  • Test the water again

You can do this after 24 hours; test your pH and the chlorine level. Your chlorine level needs to be high and pH at the ideal range. But if your chlorine level drops to zero and your pH level, not in the ideal range then it might just be time for you to bring in professionals.

Will low pH make the pool green?

Yes, it will make your pool green due to the presence of algae. Your pool is turning green because your pH level is out of balance. This will affect both the filtration system and the sanitizing chemicals. A low pH can attract acidophilic and acidotolerant algae.


One of the effects of having a low pH in your pool is creating an enabling environment for algae to form. Having algae in your pool might deter you from even swimming in it. This is because the water wouldn’t be attractive in the first instance.

Another issue is that it will always take extra effort and money to rid the pool water of complete algae. The annoying part is that when once you give room for algae to thrive in your pool, it is much easier for such to happen again in the future. Always note that having algae in your pool from whatever means will cloud and color your water.

It will make rescuing attempts difficult too, as it will reduce the depth perception of a diver. The best bet for you is to prevent this from happening. It will be a lot better for you to buy more chemicals, pay for more electricity, raise your pH level than looking out to fix the problem of algae when it blooms already in your pool. So always work on your pool pH and other imbalances to get the best out of it.

Leave a Comment