What pH Should My Betta Fish Tank Be

Aquarium pH is a measure of the acidity or alkalinity of aquarium water an important water parameter.

Your betta fish tank should have a neutral pH of around 7.0. Read our quick guide and find out what affects pH and what to do about it.

What Is Aquarium pH?

Aquarium ph is a measure of the alkalinity of water. It ranges from 1 to 14, with 1 being most acidic, 7 being neutral and 14 being most alkaline. See some graphic examples here.

The pH scale is a logarithmic scale, which means that each whole number change results in a factor of 10. For example, a pH of 7.0 is ten times more acidic than a pH of 8.0.

Aquarium fish thrive when aquarium pH is as close as in their natural environment. This can vary. For betta fish, the optimal pH is between 6.8 to 7.5. Aim for neutral pH 7.0 and you won’t go wrong.

Why does water pH matter?

You got fish, plants, and bacteria. All of them are dependent on the water’s pH. It also affects how waste is turned into toxic ammonia.

Let’s start with the silent heroes, the bacteria. Beneficial bacteria turn organic waste into harmless nitrate in what is called the nitrogen cycle. Bacteria need a ph of more than 6.5 to function properly. The optimum range for them is 7.0 – 8.0. 

Talking of waste, harmless ammonium (NH4) will turn into toxic ammonia (NH3) as pH rises. Both ammonium and ammonia are converted by ammonia-oxidizing bacteria (AOB) during the nitrogen cycle.

For fish, acidic water (low pH) can destroy eggs, damage eyes, and eventually lead to diseases and death. 

Alkaline water (high pH) will dissolve their protective mucus making them vulnerable to infections. Fins and tails will look bad. Added to that, high ammonia levels will damage their internal organs. Damaged gills will make breathing hard.

Aquarium plants need pH of 6.5 to 7.5 to thrive.

Both extremes pose great danger. Aim for neutral pH of around 7.0 which is a good compromise.

Beware that pH levels in the aquarium will gradually drop over time, mainly due to the nitrogen cycle. Test the water and do a partial water change if needed.

Natural fluctuation of PH

In nature, pH follows a natural daily rhythm that is affected by respiration and photosynthesis, which change carbon dioxide levels (CO2).

Carbon dioxide from respiration elevates the acidity of water while photosynthesis from plants absorbs carbon dioxide and lowers acidity. Since photosynthesis during the day, CO2 levels elevate during nighttime and decrease during the day.

If your tank has plants this natural pH fluctuation will occur. Nothing to worry about. It is natural and expected.

What about substrate and rocks

Sources of calcium such as limestone or shells or coral sand or dolomite gravel will gradually elevate pH.

Beware of the rocks you put and the substrate you use. Indeed, it is common to use such substances to correct acidic water.

Signs to look for

If water is too acidic you might find marks like skin burns. Fish will swim in an erratic way and will show signs of sickness.

The shells of snails will be thin and soft in acidic water.

If water gets too alkaline, you will also see your fish acting strangely.

A note on algae. If you get algae overgrowth, too much carbon dioxide will be bound disrupting pH levels. 

A sudden change in pH

Fish adapt to slow incremental changes in water acidity. On the other hand, abrupt changes might bring a condition called pH shock. Symptoms may vary from staying motionless and resting on the bottom to swimming erratic and staying at the top.  This is a serious condition and has to be immediately fixed. 

This might happen during a water change that alters water parameters too much and too fast. 

It can also happen when releasing a new fish from a bag into its new aquarium.

Or when adding chemicals without first removing the fish.

How to fix PH

Water changes are the best way to keep pH at desired levels

Driftwood release tannin, which is acidic and will lower pH.

Crushed corals and other calcium-containing substances will elevate pH levels.

If you need a faster solution, remove the fish and use additives.

Baking powder will crease the pH and lemon juice will decrease the pH. Commercial acid or alkaline aquarium buffers are available.

Be aware that such additives are only short-term solutions.

What about the water quality of the water you use? 

You should test it anyways for chemicals like chlorine. See that pH is ok too.

You can learn more about the correct water to use here.


Maintaining a proper level of aquarium ph is one of the things one has to learn.  With some testing and trial and error, finding a proper balance is not difficult.

If you want to learn more about Betta’s behavior, advice, and tips, please visit our collection of Betta Tips Articles.

About the author

Hi, I am Alex.
My passion is aquariums. I am especially drawn to betta fish. I love experimenting, learning, researching, and writing about them.

You can find the articles I wrote here

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