How To Lower pH in Aquarium? – Complete Guide


An aquarium is a fascinating addition to any home and office. Keeping an aquarium can bring a sense of calm and tranquility to the space that it is kept in. However, it comes with a responsibility to maintain the environment of the freshwater aquarium tank as close to nature as possible.

Water in rivers, lakes, and other water bodies is filtered naturally and regularly but your pet fish require constant maintenance, and for that, they depend on you. You will have to make sure that you keep an optimum water quality because it has a direct impact on the health of your fish.

One of the most important factors to maintain while having a freshwater aquarium is a balanced pH. Having consistent pH levels is part of having a thriving aquarium. It is usually set at the time of acquiring the fish tank, but usually ignored because of unawareness of water chemistry. Being fully equipped with the correct knowledge will help you maintain a healthy aquarium.

What Is pH in Aquariums?

how to lower ph in fish tank

The pH (potential of hydrogen) of water indicates whether the water is acidic or basic. Scientifically speaking, it is the measure of activity of hydrogen ions. It is measured on a scale of 1-14.

Neutral pH:

Ph level of 7 is known as neutral pH. A neutral pH is the one that is neither acidic nor basic. Pure water has a pH value of 7.

Alkaline pH:

Ph levels less than 7 i.e 1-6 is known as basic or alkaline.

Acidic pH:

Ph levels more than 7 i.e 8-14 is considered as acidic pH.

It is very important for the health of fish to have balanced pH levels in the tank. Freshwater aquariums can have different fish species from different water environments, so it is necessary to maintain pH levels that suit most of the species. Most fish tanks will thrive best in an optimum pH range between 6.8 and 7.8. It is important to note that the pH levels do not fall above or below this range.

Here is how to identify whether pH levels are high alkaline or high acidic.

High Alkaline pH in Aquarium:

Ammonia is present in the tank to feed the bacteria and keep a healthy cycle. If the water is too alkaline this ammonia can become toxic and harm fish. It can noticeably harm fins and tails of fish and affect growth and appearance. Fish can not survive in such an environment and eventually die.

High Acidic pH in Aquarium:

In the presence of highly acidic water, fish start producing more mucus on their skin in order to protect them from damage. This in turn makes it difficult for oxygen to cross through skin and gills. Symptoms include damaged or thick skin, gills and eyes, inability to breath, gasping and eventually death. 

What Causes High pH in Aquarium?

In order to ensure a high quality of life for your aquatic pets, maintaining an optimum pH level in aquarium water is most important. However, most people are unaware of the causes of high pH levels.

does driftwood lower ph

Here are some of the most important points to let you know about the causes of high pH value.

  • Tap water: Tap water contains alkaline or basic elements and metals which can increase the pH of water if added without proportion. 
  • Untreated water: Adding untreated water from sources like streams, rainwater etc can cause high levels of pH.
  • Adding Rocks: Some rocks, such as limestone, can dissolve in water and cause high levels of pH.
  • Aquatic Plants: Planted aquariums can trap carbon dioxide in tanks and cause a rise in pH levels. Similarly, too few plants can cause imbalance of carbon dioxide, resulting in higher pH levels. You can also check how to clean aquarium plants to maintain the pH level.
  • Ineffective filter: A filter is necessary to dispose off fish waste materials and fish food. If waste matter and broken-down fish food is left in water, it can increase toxicity and pH of water.
  • Baking Soda: Baking soda is usually added to aquarium to maintain pH levels but adding too much of it can increase pH.
  • Low Carbon dioxide: Low levels of carbon dioxide can contribute to high levels of ph in fish tank.

How Often Should You Test pH in an Aquarium?

Testing the pH in your aquarium is really important for maintaining an optimal environment.

how to lower aquarium ph

Before Purchasing New Fish:

Check the pH of the tank when you decide to buy new fish. Also ask the shop to tell you about the optimal pH level that the fish thrives in. Make sure that the pH of your aquarium is suited for any new fish that you decide to add.

Weekly and Monthly Tests:

The pH levels of fish tanks should be checked every month but optimally every two weeks. It is important to keep a log to identify any unusual trends before they get out of hand. Schedule a set time for every reading because the results can vary depending upon what time of the day you took the test. Day time, specifically afternoon, is suggested for accurate results.

Fish Illness or death:

It is wise to always check the pH whenever there is an illness or death of aquarium fish. It is indicative of the fact that there might be something wrong. Fish Illness or Death:It is wise to always check the pH whenever there is an illness or death of aquarium fish. It is indicative of the fact that there might be something wrong. 

Addition of Medicine to Fish Tank:

Whenever you add a medicine to your aquarium, make sure you take pH tests before the test, during the time period of medication and after it has ended. If there is any change in the pH, take necessary steps to maintain the pH in range.

When Is It Necessary To Lower the pH in Aquariums?

It is important to look for the symptoms of high pH in fish tanks before deciding to lower it down.

how to lower the ph in a fish tank

Algae Growth:
If you observe any unusual growth of algae on walls or around ornaments in aquarium, it indicates that the pH level of the aquarium is higher than needed. High pH levels promote the growth of algae and make the environment of the fish tank water highly toxic for fish to survive.

Unusual Fish Behaviour:

If you notice that your fish are acting more excited or highly active for no apparent reason, it might be due to high pH. They may also have trouble breathing.

Symptoms of Illness:

If you notice white spots on fish skin or blood streaks in their fins, it indicates a disease called ich. It is caused due to high pH. Fish may appear lethargic or scratch their skin against rocks. This disease can cause death if left untreated.

If you notice any of the above-mentioned symptoms, keep in mind that any change in the fish tank water should be gradual. You should try to reduce pH over the course of weeks. Any rapid change in environment can be disastrous for the inhabitants of the fish tank and can cause more harm than good. Make sure you take proper guidance to safely lower ph and read all the instructions on the manual carefully before implementing any change.

 How to Lower pH in Aquariums

If you have noticed any symptoms of high pH in your aquarium, you must take a pH test. If the test indicates a high pH level, it might be time to take some necessary measures to reduce pH.

how to lower fish tank ph

Regular cleaning and maintenance of the fish tank must be considered as part of the natural ways of lowering pH. 

Here are a few ways that can help you to lower the pH of your aquarium.

Chemical Solutions

Chemical solutions are a great way to lower pH in aquarium water because the effects are quick. There are many options available in the market that can be used in different dosages as per your need. They can be purchased by the names such as pH down, neutral regulator, pH minus, alkaline buffer etc. 

These solutions work by buffering and absorbing extra hydrogen atoms which cause pH imbalance. These products use bicarbonate, carbonate and phosphate to achieve the result. They are very safe for marine life and a great option to fix your aquarium pH problems.


Driftwoods can be a very attractive yet beneficial addition to your aquarium. It contains natural compounds called tannins or polyphenols that help to lower pH.

Driftwood should sink down at the bottom of the fish tank water. Consider soaking driftwood in a bucket of water for 24 hours before adding it to your aquarium. Driftwood can give the water a yellowish tint and you would need a large piece of it to take effect. 

Natural driftwood takes its effect slowly by buffering the pH, which is ideal for suggested slow change to the water.

Peat Moss

Peat moss is one of the natural methods. It releases the compounds of gallic acid and tannins into the water that lower ph.

Peat moss tends to turn the water yellow. Hence, it is best to soak peat moss for a considerable amount of time, before adding it into the aquarium.

There are various ways in which it can be used inside the tank.

  • It can be used as a substrate at the bottom of the fish tank.
  • It can be hanged inside the canister or in a small pouch
  • You can soak peat moss in water and add the water into your tank

Peat moss takes its effect slowly to lower pH over the course of weeks.

Catappa Leaves

Catappa leaves are also known as Indian almond leaves. They are useful in treating bacterial and fungal infections and are easily available at local pet store. If your fish was already showing symptoms of disease, it can help in treating and protecting fish skin. Tannin compounds in these leaves can buffer the water and help to lower the pH.

You can use these as

  • a top layer in water
  • Crush the leaves and add them to fish tank
  • Bundle them and place within the filter

Water Changes

Changing the water of your fish tank regularly is really important to maintain water pH. You can change the water once a month or every two weeks. Make sure to replace only 15-20% of water at a time. 

When you change the water, you take out the harmful compounds that are causing the pH imbalance such as ammonia and minerals. Adding neutral water can maintain balance and help to lower the pH levels. However, this is not a permanent solution if high pH levels are caused by some other reason.

Make sure to keep the following points in mind while changing the water:

  • Check pH of water before adding it to tank
  • The temperature of the water should be the same as that of the aquarium
  • Let the tap water sit for three days before adding it to the fish tank
  • Use a de-chlorinator
  • Clean the sand in aquarium tank and remove decayed matter and algae manually before adding water Reverse Osmosis Units

Reverse osmosis units are a type of water filtration system that can catch fine compounds present in water by using a fine semi-permeable membrane. It traps heavy ions such as Sulphur and lets light ions, such as water, pass through easily.

Having a reverse osmosis unit can give your tank regular filtration and remove harmful chemicals. It is a great way to tackle pH imbalance as it removes toxins.

The only disadvantage is that, along with removing unnecessary compounds and chemicals, it can also eliminate useful compounds. This means that you will have to add your nutrients regularly to maintain balance.

Final Thought

Having an aquarium can bring a lot of joy to fish tank owners, but it comes with great responsibility. Your aquatic friends need optimum pH levels to thrive. Make sure you watch out for any signs of pH changes in your fish tank. 

Pay special attention to all parts of the aquarium and notice if something is becoming cracked, old, rusty, or less functional. Test the pH regularly and take necessary actions if necessary. Make sure you follow all the instructions carefully. All the methods listed above should help you when needed. 

Cody Mitchell
Cody Mitchell is a pet lover and a passionate pet writer. He has worked as a professional writer for over 6 years, with a focus on creating compelling content for pet-related brands. His work has been featured in major publications. When he's not writing, Cody can be found playing with his two dogs (a labradoodle and a cocker spaniel) or cuddling his cat.

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