Do Aquarium Plants Lower the pH of the Tank?


The addition of plants in an aquarium may have a lot of benefits. However, it may also impact the tank’s conditions, like pH, which may affect the fish. 

Only a few aquarium plants can lower the pH of the tank. Most plants increase the pH instead when they consume carbon dioxide for photosynthesis. However, when plants die and decay, they lead to lowered pH levels. 

Plants do not have a consistent effect on pH. Depending on the type, they can either lower or increase the pH. The impact depends on several conditions, as you’ll find out in this article. 

What Is pH?

Before we proceed, it’s important to understand the concept of pH. This is a scale that is applied in daily life, not just in aquariums.

A pH level refers to the measurement of acidity or basicity in water. It is a scale that goes from 1 to 14. The lower the pH, the more acidic the substance. The higher the pH, the more basic or alkaline the item. Meanwhile, a pH of 7 is considered neutral. 

While a neutral pH seems safe for all cases, the optimal pH levels depend on the situation. 

In the case of aquariums, the best pH depends on the kind of fish and plants in your tank – whether they can tolerate extreme pH or not. 

What Aquarium Plants Can Lower the pH of the Tank?

Now that I’ve established the concept of pH, we can talk more about aquarium plants that can lower it. In other words, plants can make tank conditions more acidic.

Aquarium plants that can lower the tank’s pH are those capable of absorbing minerals and metabolizing nitrogenous waste. Dead plants can also lower the pH as they decay. Decreased pH levels affect plants and fish; thus, they must be monitored.

The metabolism of nitrogenous waste, like ammonia, may lead to lower pH because the decomposition processes of ammonia produce hydrogen ions. These ions make the water more acidic and temper the harmful effects of ammonia, like ammonia poisoning.     

What Happens to the Aquarium if pH Is Lowered?

Maintaining consistent and appropriate aquarium conditions, like pH, is crucial for fish survival. Thus, tank owners look for ways to lower pH when pH gets too high. 

Lowering the aquarium pH when it gets too high helps prevent harmful effects such as ammonium poisoning. It also helps adjust the pH to a more optimal range, depending on the kind of fish and plants present. However, careful adjustments are needed. 

Too much decrease in aquarium pH can be harmful to your aquatic life. Thus, ensure that it is at an optimal range.

Here are some effects of too low tank pH:

  • Proliferation of algae
  • Sludge buildup 
  • Sluggish and stressed fish 

What Are Other Ways To Lower Aquarium pH?

Suppose your tank is edging past the optimal pH level, and you want to lower it. However, the plants in your aquarium aren’t enough, and you can’t have anymore. 

Fortunately, there are ways to lower pH besides using plants. Use these and a pH monitor kit or probes to supervise pH adjustments effectively. 

Here are other ways to lower aquarium pH. You can use:

  • Peat moss
  • Driftwood
  • Indian almond leaves
  • Reverse osmosis 
  • Soil 
  • Alder cones
  • CO2 injection 

Do not try to lower the pH by keeping dead and decaying plants in the tank. Although it decreases pH, the waste and compounds released by rotting plants may harm the fish. 

Ways To Alter the pH of the Tank With Aquarium Plants

Besides lowering pH, aquarium plants are also capable of increasing it. Thus, the impact of having them in your tank goes two ways. But how does this happen?

These are ways through which aquarium plants alter the pH of the tank: 

  • Photosynthesis. Plants consume carbon dioxide (CO2) and produce oxygen (O2) to create their own food. When plants remove CO2 from the water, they are also removing acid. Thus, photosynthesis decreases acidity while increasing the pH level.  
  • Nitrogen metabolism. Plants are also capable of metabolizing chemicals like ammonia and other nitrogenous compounds. When they process these substances, pH levels may rise or lower, depending on the compounds and processes. 
  • Mineral absorption. Besides nitrogenous compounds and CO2, plants also consume minerals like calcium. Calcium consumption affects the water’s ability to buffer or maintain constant pH levels. This leads to a pH drop or increased acidity.  
  • Depletion of plants. The addition or loss of aquarium plants can impact the tank’s pH. Decay may often lead to lower pH levels while the addition of plants may lead to a higher pH. 

Final Thoughts 

Aquarium plants are capable of lowering a tank’s pH. However, they may also raise it through various processes. Using plants alongside other methods of lowering pH may help achieve the effect of decreased pH more successfully than plants alone. 

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