Aquarium water is characterized by several parameters, among which its pH acidity plays an important role. The acidity of tap water may not be ideal for aquarium fish, so you need to know how to check the pH and adjust it if necessary.

If you find that there is a significant difference between the pH of fresh water that has just been poured into the aquarium and older water from the aquarium (which has been in the aquarium for about 48 hours), you should take immediate action to find out why this is happening.

Basics of pH

The pH level of water is measured from 0 to 14. A pH level of 7.0 is considered neutral, values below 7.0 are acidic, and values above 7.0 are alkaline. Water pH varies depending on a number of factors including chemical concentration, mineral content and even depends on the type of substrate. Each species of fish is adapted to different pH levels - a pH value that will be fine for some fish may not suit other fish species at all. That's why it's important to measure the pH level of your aquarium before releasing fish into it.

How to test the pH of your tap water

Many experienced aquarists test tap water before putting it in the tank. However, the resulting acidity readings can be very approximate.

To properly measure the pH of your tap water, pour the tap water into a bucket and place an aerator in it to oxygenate the water. Then you need to let the water stand for 24 hours. Only then can you check the pH level in the water. The same measurements should be taken after 48 hours to make sure the pH reading is stable.

So, why should you let the water stand for 24-48 hours? Carbon dioxide in the water causes the pH to drop. The process of aerating the water mixes all the layers of the water and gas exchange occurs (oxygen enters the water and carbon dioxide is released from the water into the air). This gas exchange reduces the amount of carbon dioxide in the water and causes the pH to rise. This reading will be the closest to the real thing, provided there are no other objects / chemicals in the water tank affecting the pH, as gas exchange is constantly occurring.

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How pH affects the inhabitants of the aquarium

The PH of the water in your aquarium significantly affects both its quality and chemical composition. For example, if your pH drops below 6.0, nitrification bacteria, which stabilize ammonia and nitrite (toxic compounds for fish) at a safe level, will begin to die off. This can cause your aquarium to become uninhabitable for fish.

The concentration of ammonia in aquarium water is a combination of ammonium ions (NH4 +) and ammonia (NH3). The PH of the water reflects the proportion of the concentration of each of these two compounds. A greater concentration of ammonia (the more toxic of the two compounds) will be present in alkaline water (pH above 7.0), while a greater concentration of ammonium ions (the less toxic of the two compounds) will be present in acidic water (pH below 7.0).

Relationship between pH and kH

The kH level is a parameter of the carbonate hardness of your water. In other words, it measures the concentration of carbonate and bicarbonate ions in your aquarium water. The kH also indicates the water's ability to neutralize added acids without significantly changing the pH. Therefore, a higher kH corresponds to a more stable pH in your aquarium, while a lower kH can correspond to large fluctuations in pH. As a rule of thumb, if your kH is below 4.5o dH, you need to monitor your pH closely.

Water pH test kits

The best option for measuring the pH level of your aquarium is to purchase a water test kit. You can purchase one from your local pet store or order one online. Kits come in a few different forms: some use an analysis of the water by its color compared to a test sample. Other kits use litmus paper, which is dipped into the water sample being tested and then compared its color against a chart. Unfortunately, this measurement option does not always give accurate results.

It is also necessary to take into account the expiration date of the test kits (usually 6 months) and if it is expired, you can get inaccurate results. When conducting tests, it is necessary to strictly follow the instructions.

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Ways to increase pH

Let's say right away that it is much easier and better to gradually accustom fish to the pH of tap water than to constantly adjust its acidity. Nevertheless, in some cases it is necessary to correct the acidity of the water in one direction or another. There are several options for increasing water acidity levels.

• Changes in the water

Over time, the pH in your aquarium will drop. The most effective way to bring it back up to the level of your tap water is simply to change it regularly. Periodically siphoning the soil of uneaten food and waste will significantly slow down the pH drop over time.

• Rocks or substrate

Add some rock or gravel to the aquarium that will raise the pH. For example, crushed coral is used as a substrate in many African cichlid aquariums (African cichlids prefer high pH). Limestone and fossilized coral also have this property. If you do not want to add these rocks to your aquarium, you can add crushed coral to the filter element of your water filter, but be very careful, using this method can raise the pH level well beyond the acceptable value.

• Aeration

Increasing the concentration of oxygen in the water leads to a decrease in the concentration of carbon dioxide. As discussed above, less carbon dioxide leads to a higher pH value. Therefore, you can increase the aeration in your aquarium to increase the pH.

• Adding baking soda

Adding baking soda to the water will raise the pH, but remember that in this case the baking soda will need to be added to the water constantly, you can't just add it once and forget about it. When dissolving the baking soda in the water, you must be strict with the amount, as such actions can lead to the death of all your fish. The general rule of thumb is 1 teaspoon per 20 liters of water. Before adding baking soda to the aquarium it must first be dissolved in a small amount of water and then poured into the aquarium.

Ways to lower pH

Lowering the pH in a freshwater aquarium is often much more difficult than raising it. There are some options for lowering acidity that you can try.

• Filtration through peat moss

Filtration through peat moss is the most effective way to lower pH. Some aquarists use peat moss in their substrate, which has a similar effect.

• Add carbon dioxide (CO2)

As we've said several times, increasing the concentration of carbon dioxide in the water lowers the pH level.

• Snags

Many types of driftwood lower the pH.

• Chemicals

There are many chemicals on the market today that lower pH. However, like chemicals that raise pH, they do not stabilize pH.

Summary

Even though your aquarium fish prefer the pH level to which they are accustomed in nature, it is more important to have a stable pH. Constantly adjusting the pH level in your aquarium will do you no good, as pH fluctuations of as little as 0.3 units can be dangerous for your fish. Therefore, unless you have a special reason to do so, it is better to acclimatize your fish to the pH level of your tap water than to constantly adjust the pH.