What Causes pH To Rise In An Aquarium?

The pH of an aquarium is one of the most critical parameters that can affect the overall well-being of aquarium fish. An increase in pH means an imbalance in the acid-base ratio of the aquarium. Several factors can cause the alkalinity of the aquarium to rise, consequently leading to a rise in pH.

What Causes pH To Rise In An Aquarium? Mineral salts such as calcium present in some tank materials like limestone and some shells will increase the alkalinity and pH of aquariums. Other causes include; tap water, not changing filters, hardness or softness of the water and reduction of carbon dioxide in the tank.

What Causes pH To Rise In An Aquarium

Allowing excess oxygen in the tank or exposing aquarium water to air can lower the amount of carbon dioxide present in the tank. The consequence of this is that the acidity of water caused by carbon dioxide will reduce, and it will have a similar effect on the pH of the tank.

What Is the Optimum pH For Aquarium?

pH is one of those parameters that can easily affect your aquarium fish at the slightest change. It can stress them out and make them vulnerable. However, keeping the pH of a tank at an optimum level is quite easy, and the optimum temperature for the tank can vary depending on the preference of members of the fish tank.

If you operate a freshwater aquarium, it is best to keep the pH level from neutral to low [5.5-7.5]. This range is particularly suitable for most species of freshwater fish.

Likewise, a saltwater aquarium can still be at an optimum level for a pH range between neutral and a higher pH [7.5-8.0]. You should maintain the pH depending on the preference of the specific fish type.

You can also vary the pH of the aquarium depending on the hardness or softness of water. Hard water is capable of raising the pH of the aquarium. Therefore, if you don’t intend to raise the pH of your tank with the introduction of hard water, you can put the hard water through a filter to lower the pH.

You can, however, be unbothered in case you intend to use the introduction of hard water to raise the pH as in saltwater.

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It is best to keep the pH of water at an optimum level. Therefore you should take checkup steps seriously and fix any pH imbalance as soon as possible.

Nevertheless, most fish cannot cope with drastic changes in the water level of the tank; therefore, a gradual transition is instead encouraged.

Also, if you don’t lower the pH of your aquarium on time, it can cause the death of fish. This extreme consequence is because ammonia and other chemical levels generally increase with pH. Most fishes no matter how hardy they are.

Effective Ways You Can Lower The pH Of Your Tank

There is a considerable need to regulate the pH of a tank to suit the need of the tank members. You might have to either increase or lower the pH level as the case may be. However, it is often more challenging to lower the pH of a tank than increase it. Here are some effective methods that can help you reduce the pH of your fish tank;

  • Add Carbon dioxide: Increase in the amount of carbon dioxide in your tank will lead to a decrease in your pH. This decrement is as a result of the acidic nature of the mixture formed when carbon dioxide dissolves in water. You can consider pumping in more carbon dioxide into your tank if you discover that the pH is too high. You can also increase the amount of carbon dioxide in your tank by adding live plants to the aquarium.
  • Add Driftwoods to Fish Tank: Many types of driftwoods are capable of lowering the alkaline of a tank. They consequently reduce the pH of the fish tank. This method works because driftwoods will soften the water.
  • Addition Of Chemicals: Several chemicals are suitable for aquarium use that is effective in lowering the temperature of your tank. These lowering chemicals work similarly with those that increase the pH of the container. It is, however, essential to note that these chemicals cannot maintain a stable pH.
  • Filter The Water Through Peat Moss: another effective way of lowering the pH of a tank is by filtration through peat moss. Peat moss also has the same effect of pH lowering even when they serve as substrates.

Effect of High pH level on Aquarium Fish

Fish can react even to the slightest change in the pH of their tank. They often give a more lethal reaction to a drastic or rapid change in the pH. The high pH of the container means the fish are living under alkaline or essential water.

The effects of pH on fish vary, and it can have a severe impact on the overall health of the affected fish. Young fish or fry are particularly more responsive to pH change than the adult fish. The results of high pH in tanks include;

  • It can chemically burn or chap the skin of your fish.
  • It can cause your fish to dart back and forth in the tank, consequently leading to stress.
  • It can kill off the eggs of fish by preventing them from hatching.
  • It can cause gradual but noticeable deterioration in fish life.
  • In extreme cases, drastic change or high pH in a freshwater aquarium can lead to the death of the affected fish.


pH is one of the most important factors to consider while setting up your aquarium tank. The pH of a tank can either be high or low. The pH level is dependent on fish types and aquarium members. However, the key to tank pH is stability.

Even adult and healthy fish will react to the slightest or noticeable change in their tank. A drastic change in the pH of the container can be so lethal that it can lead to the death of some members of the fish population. However, a regular check and simple regulation of pH can keep everything under check and balance.



Hello, I'm Jason. I'm the guy behind HelpUsFish.com. I volunteer at my local fish shop and I created this site to offer tips and advice on the fish I care for.

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