betta fish in aquarium with full water

Betta pH: The Correct Range Level

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pH can be a little difficult to understand as it has to do with the chemistry and reactions that take place in water as a solution. However, pH is a critical aspect of keeping a healthy aquarium system and governs the oceans, rivers, and lakes of the world. pH is easily influenced by other water parameters and should be regularly monitored and recorded within the aquarium.

In this guide, we’ll discuss everything you need to know about pH, why it’s important, how it’s calculated, and the best pH range for your betta fish tank.

What is pH in the aquarium?

In the simplest terms, pH is the scientific scale for measuring the acidity or basicity of water; 7.0 is the neutral pH level for water on the pH scale of 0.0 to 14.0. Values lower than 7.0 are regarded as more acidic while values above 7.0 are regarded as more basic (also known as alkaline).

In general, freshwater aquariums require a pH level between 5.0-7.0 (with cichlids and some other species being an exception) while marine aquariums require more specific values between 8.0-8.4.

How is water pH calculated?

In order to understand pH, we need to look at some chemistry. Let us first understand water as H2O. In translation, this means that there are two hydrogen atoms (H2) bonded to one oxygen atom (O); the bond is a covalent bond where the electrons of each hydrogen atom are shared with those of oxygen.

While H2O is usually stable, occasionally, a hydrogen ion (H) or hydroxide ion (OH) will break away from the compound. When H2O separates, it can become H+ and OH. A greater concentration of H+ in the solution represents greater acidity; a greater concentration of OH in the solution represents basicity. A neutral 7.0 water pH at 77° F (25 °C) will have equal concentrations of H+ and OH.

When it comes to actually do mathematic calculations in regards to pH, the equation is pH=-log [H+]; don’t worry though, a liquid pH test kit will take out all the math! However, it is important to understand that since pH is logarithmic, this means that any fluctuations that occur are larger than you think and can have a devastating effect on your tank system.

For example, if your betta fish does best in neutral water with a pH of 7.0 but your aquarium is reading 8.0, then conditions are 10 times too basic; if your tank water is reading 9.0, this then actually means that your aquarium pH is 100 times too basic for your betta fish to handle. You can see why pH is such a huge parameter to get right for your betta!

What influences pH in your betta tank?

Simply put, basically every aspect of your aquarium influences pH, from your choice of decorations to aeration to the levels of other water parameters. In this article, we’ll only discuss a few of the parameters that can greatly affect pH.

Carbon dioxide

 When atmospheric carbon dioxide (CO2) enters the water, it becomes carbonic acid (H2CO3); however, carbonic acid does not stay in this state for long. Carbonic acid (H2CO3) will then dissociate into hydrogen ions (H+) and bicarbonate ions (HCO3). Since hydrogen ions (H+) are entering the solution, this means that the water will become more acidic and thus result in a lower pH.

In simplified terms, an increase in atmospheric carbon dioxide (CO2) will result in more acidic tank water conditions. For aquariums, this means that pH may slightly rise when windows in the house have been closed for longer than usual, and/or surface gas exchange is lacking.


KH is a much less-known water parameter, but critical for understanding how pH works in the betta aquarium; KH stands for carbonate hardness (also known as alkalinity, not to be confused with alkaline) and is the scale for determining how well water can absorb and neutralize an acid; in general, a higher KH will mean that pH will remain more stable, while a lower KH may result in instability and large pH swings.

In terms of chemistry, KH is the measurement of bicarbonate (HCO3) and carbonate (CO32-) ions in the water. In short, KH can be thought of as a buffer between the acids in your betta fish tank from having an immediate effect on pH. When attempting to increase or decrease pH in the aquarium, KH will need to be considered as a tank with a wrong KH level can make things difficult to adjust.

Note: KH is not the same as GH. GH stands for general hardness which is the measurement of certain metal ions, like calcium and magnesium; GH does not influence pH as much as carbon dioxide or KH, and more specific ions will need to be added to the water to have an effect on the system. Also, KH is recorded in terms of dKH or °KH while GH is reported in terms of dGH or °GH.

It is important to remember that these parameters do not work independently from each other. Every parameter in your betta tank is affecting another, with carbon dioxide, carbonate hardness, GH, and pH all working together to create a balance; this is why it is recommended to test tank water for all these parameters and not just one.

Why is pH important in your betta tank?

close shot of betta fish

Most beginner hobbyists are warned about the dangers of ammonia, nitrite, and nitrate to your betta, while pH is usually prescribed with a quick dip test kit and nothing more. The truth is that pH is one of the more silent deadly killers of the aquarium, and maybe one of the last water parameters you think about checking when your betta fish appears to be ill; you need to know just as much about pH as all the other parameters to make sure that your betta is living its best possible life!

Ammonia and ammonium

Ammonia (NH3) is one of the more immediate damaging parameters in the aquarium, and no fish should ever be thrown into a newly-setup betta fish tank or otherwise placed in a system that has known amounts of ammonia; relatively high amounts of ammonia can burn the lungs of bettas until the fish can no longer breathe properly and drowns.

However, there is another form of ammonia that is not as toxic to fish, ammonium (NH4). Both ammonia and ammonium are often the result of a new water cycle, overfeeding, or overcrowding that leads to an excess of waste entering the system. pH levels will determine if the waste becomes ammonia or ammonium, dictating if the tank environment will be toxic or not toxic.

Simply put, lower pH will result in a higher concentration of ammonium (NH4) while a higher pH will result in a higher concentration of ammonia (NH3); as pH rises, the toxicity of ammonia will also rise. For those amounts of ammonia that enter the tank water, established nitrifying bacteria should be able to quickly complete the process into nitrites and nitrates if the pH is at an ideal level. If ammonia enters an uncycled tank, nitrifying bacteria will have a difficult time making these conversions quickly, which can lead to ammonia/nitrite poisoning for your betta.

Incorrect pH levels

Both acidic and basic pH levels can prove to be devastating for fish. At both ends of the spectrum, pH can chemically burn the externals and internals of betta fish and other invertebrates. Higher basic levels also pose the threat of fostering excess amounts of ammonia, which can lead to a very painful death for the betta fish in your tank.

Different species of fish come from different parts of the world and are all physiologically adapted to certain water conditions and parameters. A correct pH keeps the anatomy and internal functions of betta fish and invertebrates working how they should.

How does pH change throughout the day in your betta tank?

You may have noticed that your pH changes from the morning to the night, especially in a heavily planted tank or reef tank system. Don’t worry, this is completely normal and is a result of photosynthetic and respiration.

Throughout the day, fish, invertebrates, and other non-photosynthetic organisms go through respiration, creating carbon dioxide within the water column. Plants, zooxanthellae in corals, and other photosynthetic-dependents take up and process that carbon dioxide into oxygen throughout the day; these organisms are also respiring throughout the day and night, but photosynthesis is the more outstanding process when the sun is out. The resulting pH is a reflection of the constant balance between photosynthesis and respiration rates happening within the tank, with carbon dioxide levels having a major influence on pH as discussed earlier.

In most ecosystems, photosynthesis is the dominant process, removing much of the available carbon dioxide and ultimately raising pH. As the sun sets, the rate of photosynthesis decreases until eventually stopping when it is night, and pH begins to fall. These light-dependent organisms also continue to contribute to the total amount of respiration at night along with other aquatic life.

In short, pH will be higher during the day as opposed to night due to photosynthesis–and subsequently, the uptaking of carbon dioxide–occurring only when the sun is out. Usually, these processes remain in balance and pH will only shift a little throughout the day and does not need to be monitored.

However, if you’re experiencing a plant or algae outbreak in your indoor tank or outdoor pond, it might be worth watching. This is because excess plant and algae growth can take up more carbon dioxide than is being generated from respiration, resulting in higher pH levels throughout the day and possibly into the night. This problem will continue until photosynthesis rates decrease or respiration rates increase by pruning plants and/or removing algae.

If your tank is inside, also make sure to monitor the lighting period as extended amounts of light can also lead to exponential plant and algae growth that subsequently increases pH.

What is the best pH for betta fish?

Now that we know what pH is, why it’s important, and what affects it, what is the best pH level for your betta fish tank? Luckily, betta fish are pretty hardy fish but a stable pH is still essential.

Betta fish do best with a neutral pH level of 7.0 but can tolerate a range between 6.5-7.0. For everything, you need to know about how to take care of your betta fish, make sure to check out our beginner’s guide here.

Are betta fish sensitive to pH?

Betta fish are a pretty hardy aquarium species and are tolerable of some fluctuations in water parameters. However, as discussed before, higher pH levels can result in higher levels of ammonia which can quickly reach toxic levels; lower pH levels can also quickly damage the external and internal surfaces of your betta!

Though betta fish do best in a pH range between 6.5-7.5, stability is more important than ‘correct’ numbers. At the same time, a betta fish shouldn’t be kept in overly basic or acidic water. For this reason, it is usually not recommended to use chemical solutions to fix pH problems as they can cause large and unpredictable water parameter changes.

As we’ll discuss later, it is usually recommended to use distilled water or reverse osmosis (RO) water to have better control over pH in your betta tank. Tap water can have varying pH, KH, and GH levels that might need to be chemically altered otherwise. If your tap water has consistent parameters, always make sure to use a water conditioner; the water conditioner should also be used on distilled water and RO water just for extra security as well.

How do you check the pH level of your betta tank?

With all this water chemistry, checking the pH level in your tank might seem intimidating. Luckily, checking your pH is just as easy–if not, even easier–than checking the other major water parameters of your betta fish tank. There are three main options you will have when purchasing a pH test kit: paper test strips, liquid tests, and digital tests.

Paper test strips

Arguably the cheapest yet worst option, paper test strips are regularly sold in local aquarium and pet stores. These tests are fast and easy to use but incredibly inaccurate.

These tests work by having to dip the paper test strip into the aquarium water and then matching the resulting color to a set of colors with corresponding pH value. However, these colors can be very difficult to differentiate from each other and often have large intervals; pH levels are usually recorded to the nearest hundredth of a decimal while some of these paper tests only test to the closest whole number! Remember, pH is measured on a logarithmic scale and these intervals are actually much larger than they might appear in the numeric form!

Not only are these pH paper test kits difficult to read, but they often become inaccurate very easily due to environmental influences. Age, sunlight, temperature, and even exposure to air can affect the accuracy of the reagent within the strip, rendering them useless. In practice, these types of test kits don’t really help at all!

Liquid tests

If you have an average betta fish system, a liquid pH test kit is probably the best choice for you; they’re relatively accurate and easy to perform.

Liquid tests require a small amount of tank water for one or two reagents to be dropped into, which will then cause the solution to change color; this color then needs to be matched to a defined color with corresponding pH value. The instructions are usually very clear and pH readings are usually immediate. However, the same problem arises with having to differentiate between close colors, though the intervals are usually much closer and more precise than those of paper test strips.

Liquid test kits usually have an expiration date within 2-3 years of purchase and still require some special storing. Still, their shelf life seems to be much better than that of paper test strip kits.

Digital tests

If you have the means, digital pH testers are best for measuring water parameters. These devices give exact number values without having to match colors, but the initial expense of the tester can be expensive and calibration solutions can also become costly.

There is also a lot more to break on these testers, and extreme care should be taken when using them and storing them. Some hobbyists have also had trouble with calibration as sometimes the calibration solution is faulty and/or outdated, resulting in false readings. However, digital tests still provide the best accuracy for telling your exact pH level in your tank.

How do you lower the pH in your betta tank?

If you’re having problems with pH, there may be a serious underlying issue in your aquarium and/or with the source water you are using. If you’re struggling with a high pH or if you are also keeping fish that prefer a more acidic environment, there are luckily a few natural ways to help bring it down to more favorable values.

Remember, it is never recommended to immediately resort to chemical fixes as these often serve as temporary fixes for a much larger problem occurring in the tank.


Tannins are naturally found in some species of the plant kingdom and are used for protection against bacterial and fungal agents. When these plant species are placed into the tank, these tannins are released as a weak acid that discolors and softens the water; since this is essentially adding an acid to the tank (more H+), the water becomes more acidic, lowering the pH.

Some common methods of introducing tannins into the aquarium are by way of Indian almond leaves, driftwood, or peat moss. Tannins are also said to increase fish immunity which can help keep your betta fish healthy and happy.

Decrease aeration

High pH levels could be the result of not having enough carbon dioxide in the tank system; this could mean that there are too many live plants producing oxygen through photosynthesis or that there is too much surface agitation that is subsequently introducing too much atmospheric oxygen.

A balance needs to be created between the oxygen and carbon dioxide present in the system. Either pruning back live plants or decreasing surface agitation could help lower carbon dioxide levels, also lowering pH levels; it may also be worthwhile to look into dosing carbon dioxide if you are running a heavily planted tank as this will help maintain pH while still promoting plant growth.

Source water

There is a reason for low pH happening in your betta fish tank. Sometimes it is the result of the natural processes within your tank, but most times it is caused by the pH of the source water being used.

It is highly recommended to test source water every so often to make sure that the levels are desired and to later understand how the water is being processed once integrated into the tank. These levels should be tested every month or so and every time a new water source is used. Most times, distilled water and reverse osmosis (RO) water will have a neutral pH of 7.0, though this should not be assumed as a constant.

If using tap water, it will be more difficult to fully understand your pH and more regular testing will need to be done. Tap water pH is largely based on the geology of the reservoir in your region. In most areas, the accepted pH range is 6.5-8.5. Areas with more concentrated levels of carbonate and bicarbonate in the landscape will cause a higher, more basic pH. However, tap water pH may also be influenced by other factors, such as rainfall, plant decomposition, and runoff, resulting in varying pH levels depending on the season or other environmental conditions.

Many hobbyists prefer using pure water, like distilled water or RO water, to keep the pH at a known and desired level. If you’re currently using tap water, it may be worthwhile to either test the pH level yourself or have it sent for an inductively coupled plasma (ICP) analysis for a more comprehensive reading of your water. Even then, you may have to switch over from tap water to distilled/RO if your water naturally has a high pH level.

In order to make this switch from tap water to distilled/RO, small water changes should be performed weekly until all the water in the tank has been incrementally switched out. This should help lower the pH at a less stressful rate for your betta fish.

It is also important to note that some tap water may have an appropriate pH level but a higher KH level. This can make it difficult to make changes to the pH level if needed. Distilled water and RO water should have a KH level of 0 dKH, making it easier to adjust pH accordingly.

Vinegar and other chemicals

If naturally introducing tannins, decreasing the oxygen level within the betta tank, and switching source waters isn’t possible, it might be time to add some vinegar to your tank water. However, adding vinegar is a temporary solution to a bigger problem and is not a recommended method of treating high pH.

The best vinegar to get for lowering pH is commercial distilled white vinegar; it should be labeled as 5% acetic acid or 5% acidity. 1 mL of distilled white vinegar should be added per gallon (3.79 L) of tank water. It is best to slowly add this 1 mL to an area of high flow and as far away from your betta fish and other livestock as possible. This process should lower the pH by about 0.3 with every dosing. Some hobbyists choose to do this right before the tank lights go out as this is one of the times that pH is at its highest. Repeat this process daily until the underlying problem has been solved.

Again, adding commercial distilled white vinegar is not recommended unless an emergency. Most times, it is much easier to just mix tap water with distilled or RO water if large amounts cannot immediately be obtained. This same principle also applies to the use of chemicals to lower the pH.

How do you raise pH in your betta tank?

Raising pH levels in your betta tank is a little easier but should still be taken as a slow and steady process. Some of the popular methods include increasing aeration, water changes, baking soda, and adding crushed coral.

Increase aeration

While you want to decrease aeration with a high pH, you will want to increase aeration for a tank with a low pH. Some ways to do this would be by increasing surface water agitation, introducing more live plants, adding an air stone, or opening more windows.

Increasing surface water agitation and adding an air stone will introduce oxygen directly into the tank. More live plants will help take-up more carbon dioxide and replace oxygen within the system. While these are two easy ways to increase aeration throughout the tank, your betta fish tank might already have sufficient surface water agitation or your tank might not be set up for live plants. In this case, an air stone or something as simple as opening the windows might work instead.

An air stone will pump in oxygen from outside the tank. However, this air is only as rich in oxygen as the air is in the current room. As mentioned before, carbon dioxide levels tend to increase during cooler days when windows are closed. While it is unlikely that this is the main cause of a low pH in your tank, it is certainly not out of the question.

If you find that your low pH correlates with the opening and closing of your windows, it might be worthwhile to occasionally leave a window open for a couple of hours every now and then to replenish the oxygen in your tank.

Water changes

Water changes help introduce new oxygen into your betta tank and remove wastes that could be influencing the pH.

When performing a water change, gas exchange is occurring due to increased surface agitation and by way of new water. Water changes will also help remove and replace carbon dioxide that may have been used by your fish and invertebrates in your betta tank, especially if you don’t have live plants that will process the carbon dioxide for you. Water changes will also help remove and replace trace elements that could also be influencing pH.

However, if you’re struggling with a low pH, it is best to use a test kit on your source water to make sure that the pH is an acceptable value; if it’s the same value, your pH will stay the same. A small 15-10% water change should be performed weekly to keep the pH from rising too quickly in your tank.

Use crushed coral and other substrates

Coral relies on carbonate to make calcium carbonate (CaCO3), which is the basis for their skeletons; crushed coral is usually a mixture of limestone, pieces of coral skeleton, and shell. When placed in an aquarium with low pH, crushed coral will quickly dissolve and buffer the KH by releasing the calcium carbonate into the water; this rate of dissolution will slow once the pH begins to rise. Over time, KH will rise and pH will follow.

Most hobbyists like to use crushed coral as their filter media, though it is better to be used as a substrate if keeping fish that prefer high pH all the time. Crushed coral can take quite a while to dissolve completely, and will only need to be replaced about once every one to two years. Water changes may also need to be performed during this time to help pH raise to the preferred levels. Note that crushed coral can be difficult to monitor as it is unknown how quickly and how much it will affect KH and pH. It is best to add it slowly and to use a test kit to check water parameters regularly.

Some other popular options are aragonite or dolomite, though each one has its advantages and disadvantages in a betta tank system.

Crushed coral

Crushed coral as filter media works well, slowly releasing calcium carbonate into the tank water and raising KH and pH. However, it can trap a lot of detritus and will need to be cleaned regularly. The same problem tends to occur when used as a substrate, in which case, it will need to be regularly vacuumed.

It is important to note that crushed coral can also be sharp, especially if the substrate is brand new. This could result in injury to a particularly lazy betta that likes to sit on the bottom of the tank or even a betta with long finnage. On top of that, most hobbyists have found the appearance of crushed coral to be outdated and have moved onto the much sleeker and natural-looking aragonite sand.


Aragonite sand is the preferred tank substrate for aesthetics because it is as natural-looking as it can be. Aragonite sand is weathered and crushed calcium carbonate matter and will act the same way as crushed coral does in terms of KH and pH.

Aragonite sand can be placed in the filter, but also catches a lot of detritus; if the water gets kicked up, it can also cause the sand to become unsettled which can lead to cloudiness and damage to aquarium equipment. As a substrate, it is one of the most appealing types, but can also be kicked up and lead to the cloudy tank water. Aragonite sand will also move with the water current in your betta tank, sometimes leading to bare areas or spots with too much piled up.


Dolomite is made up of calcium magnesium carbonate CaMg(CO3)2. Dolomite is a little outdated as a substrate too but might be your preferred choice if you’re looking for a magnesium source for your betta tank. However, dolomite has a slightly lower dissolution point than aragonite, meaning that for especially low pH values, dolomite might be more immediately effective.

Dolomite is a little more coarse than aragonite sand, and could potentially hurt betta fish if scratched against.

Baking soda and other buffers

Like vinegar, baking soda should be a last resort to increasing the pH in your betta tank. If all else has failed–increased aeration, more frequent water changes, and substrate media–and you’re still left with a low pH in an emergency, baking soda might just hold your betta tank over until the true underlying problem can be found.

Chemically, baking soda is sodium bicarbonate (NaHCO3) and alkaline. As more bicarbonate enters the water, KH rises, creating a more stable range for pH to follow. In general, it is recommended to dose 1 teaspoon of baking soda per every 5 gallons of tank water; however, it is much better to go slower than too quickly as your betta fish still needs to adapt to the logarithmic scale of pH.

Of course, there are many commercialized products available that can also raise pH, but they’re often more expensive than baking soda and just as temporary. If you choose to go with another product, make sure to regularly check the water with your test kit and find the underlying problem as fast as possible.

Should you try for an ideal pH for your betta fish?

close shot of blue betta fish

If your betta tank is happy, don’t try to fix it. You might not ever figure out what the cause is behind your pH being out of the ideal range for your betta fish, but that doesn’t exactly mean that your betta is suffering in any way.

It is important to keep in mind that betta fish have, unfortunately, been bred and kept in less-than-ideal water conditions for decades. While this isn’t preferred, betta fish have shown that they can adapt to a variety of water conditions as long as they are stable. In general, all aquariums do better when water parameters are stable as opposed to when ideal numbers are being chased; in some cases, ideal numbers don’t even lead to a perfect tank or happy betta!

If you are doing everything that you can to make your tank as hospitable for your betta fish are you can, and your betta fish doesn’t seem to be suffering in any way, then don’t try to fix it. However, just keep a close eye on all parameters and watch how they interact with each other; if one starts to change drastically, then it is time to take a closer look at the chemistry of your water.

But if your betta fish is happy, then that is all that matters in the end!


pH is a pretty complicated aspect of water chemistry but determines the overall health and stability of your betta tank. This logarithmic parameter can either be low (acidic), high (basic), or neutral (7.0) and changes throughout the day due to photosynthesis and respiration. Betta fish require a pretty neutral pH, which will need to be measured with a test kit regularly, whether by a paper test strip, liquid test, or digital reader.

There are many ways to adjust pH if it becomes too high or too low, but it is important to understand the main source of the problem, whether it be a lack of aeration in the tank or not enough water changes. pH can quickly affect betta fish otherwise and might not be the first water parameter you think to check first!

If you have any questions about the water chemistry behind pH, your betta fish, and pH, raising or lowering pH, or if you have had experience dealing with betta fish and water pH before, don’t hesitate to leave a comment below!

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