How to lower pH in Aquarium?

How to lower pH in Aquarium? 10 Easy Methods

Keeping your fish aquarium is an adventurous and satisfying experience. To achieve
perfection in this field, you must pay attention to the needs of your fish. If you are already a
fish keeper or owing to become one, then you must remember that maintaining balanced and
stable water conditions is paramount in fish care.

The most common mistake committed by beginners in fishkeeping is that they forget to check
and maintain water parameters regularly. This mistake eventually proves fatal for their fish.
Important water parameters include water temperature, water pH, KG, GH, water hardness,
nitrate, nitrite, chloride, phosphate, and ammonia levels in the water. Every fish has its
requirements in terms of these parameters and establishing appropriate and stable conditions
is essential for your fish’s life and growth.

Here in this article, we will be discussing what pH of water is? Why maintaining pH is
essential? What is the appropriate pH for some fish? How can you keep a stable pH in
Let’s dig into this without any delay.

What is pH?

pH is a unit that determines how acidic or basic water, or any solution is. pH is a rather important parameter as it reflects the chemistry of the water. It ranges from 1 to 14, with 7 being the neutral one.

pH less than 7 means solution is Acidic. pH 7 means the solution is neutral.

pH more than 7 means solution is basic or alkaline.

It is simply a measurement of the relative concentration of hydrogen ions (H+) and hydroxide ion (OH-) in a solution. It is a set value for every solution.

The pH of a solution measures its quality, and it also controls the nutrient availability, activity of microbes, biological reactions, and behavior of different chemicals.

What is the ideal pH for Aquarium?

Like any other solution, aquarium water also has a set value of pH according to its inhabitants. The most suitable pH for a freshwater fish aquarium is between 5.5-7.5 that is acidic. At the same time, a stable pH for a saltwater fish aquarium is 7.6-8.4 that is alkaline.

A change of pH from 4 to 5 actually has ten fold effect. Thus, even a slight change in pH means a drastic and life-threatening change in Aquarium. So, it is vital for aquatic life to maintain an appropriate pH.

Stable pH for some of the freshwater fish is given below.

The stable pH for some of the saltwater fish is stated below.

  • Clownfish pH: 7.8-8.4
  • Damselfish pH: 8.0-8.4
  • Yellow tang pH: 8.1-8.4
  • Royal gramma pH: 8.1-8.5
  • Rusty angelfish pH: 8.1-8.4

Thus, you can see that the ideal pH for a freshwater Aquarium is acidic and below 7, whereas it is basic or alkaline for a saltwater aquarium.

why maintaining pH level in aquarium is important?

When do you need to lower water pH in Aquarium?

There are ways defined by nature in a natural ecosystem that help maintain stable pH and other water parameters. Many factors disturb the pH, temperature, water quality, and other essential water parameters in aquariums, ponds, and artificial fish tanks.

Thus, a fish keeper to check on these parameters and notice any disturbing changes in their fish. For example, if you see your fish getting sick, moving slowly, or showing any irregular movement or symptoms, you quickly need to check the pH of the Aquarium.

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Many factors lead to increasing water pH in aquariums. The main contributing factors are the following.

Tap water:

Using tap water is the main reason behind the increase in water pH. Tap water is rich in minerals, and it also easily dissolve substances from the surrounding atmosphere. Certain gases in the air can get readily absorbed in water and ultimately make it alkaline.

Aquarium decorations and rocks:

Most of the aquarium decorations consist of limestone that contributes carbonates and bicarbonates to the water. Moreover, rocks or crushed coral also have abundant minerals. A condition called “Carbonate hardness” develops in the fish tank.

As these carbonate ions are notorious for their alkaline nature, they significantly increase the pH of the water and disturb the water quality for fishes to survive.

Waste products:

Most of the time, an excessive amount of fish waste also plays a vital role in increasing water pH. Many substances in this waste are alkaline and are responsible for making water alkaline.

In any case, when the pH of water exceeds the desired value, you have to bring it back to the suitable level, or it will be detrimental to the health of your fish. For example, the proper pH for Oscar fish is between 6.0-7.2; if the pH of water is greater than 7.2, you should lookout for ways to decrease it.

10 Proven and Easy Methods for Lowering pH of water in Aquarium:

Freshwater Aquarium requires neutral to slightly acidic pH, and saltwater aquarium requires alkaline pH. Following are the best-proven methods to decrease pH to the desired value without affecting the health of the fish.

1- Regular Water Changes

Regular water changes are the solution to several Aquarium related problems, and it is proved beneficial in lowering the pH of water. The right way to perform these changes is to remove 25% to 50% of aquarium water and replace it with fresh water.

Freshwater is recommended as tap water actually contains lots of impurities, minerals, and carbonates that increase water’s alkalinity. Moreover, as this tap water evaporates, it leaves behind harmful minerals, and these agents keep piling up in your Aquarium. This leads to dangerously high levels of pH in the fish tank.

Thus, using freshwater is one way to combat this situation. Furthermore, regular water changes ensure the adequate removal of fish waste and food particles. These wastes are storehouses of ammonia, an agent responsible for alkaline pH. These water changes should be performed every two weeks to ensure stable pH.

So, regular water changes paired with the use of freshwater are the key to stable pH.

2- Effective Filtration system

Sometimes the water filtration system is not efficient enough to clear all the impurities and waste in the Aquarium. Thus, using the right filter is inevitable. Filters can cleanse all the extra fish waste and food particles, thus lowering the ammonia and harmful minerals and ultimately lowering the pH.

A valuable part of an aquarium filter is the “filter sludge or filter muck.” There are useful bacteria embedded in the muck responsible for removing waste products and maintaining the pH within the desired range. Thus, a clean and efficient water filter is necessary for establishing the correct pH.

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3- Using Co2 Reactors

It is a known fact that Co2 is acidic, and it contributes to decreasing the water pH. Thus, using Co2 reactors is one fast and effective way of lowering the water pH. In a planted aquarium, Co2 reactors work the best as they help the plant perform photosynthesis.

So, using a Co2 reactor is a win-win situation both for lowering water pH and plant growth.

4- Chemical Agents and Solutions

Chemical agents and solutions are the most commonly used and most beneficial methods for lowering the pH of the water to desired levels. There are many products available in the market under the name of water softeners or pH reducers. Such agents consist of acidic or high pH solutions that decrease the alkalinity of water.

These chemicals can be hazardous for your fish if not used properly. Thus, it is paramount to use the product according to the provided instructions. Even a slightly increased quantity of product can prove deadly for your fish.

5- Using Driftwood

Driftwood is believed to be a natural water acidifier because of its essential component, the “Tannins.” Tannins are acidic, and it helps reduce the alkalinity of water. Driftwood is naturally found in ponds and lakes, and it is an essential component in balancing the pH of water.

The best variety of driftwood recommended by aquarists is “The Manzanita Driftwood.” It only needs to be cleaned and scrubbed once, and then it is set for use. Moreover, Malaysian or Mopani driftwood is also one of the most widely used driftwood.

All you need is a big loaf of driftwood; clean it well before adding it to the tank. Store-bought driftwood is already prepared for aquarium use, so they don’t need further cleaning. But, if you collect it from somewhere else, you should first remove its bark and then boil, or air dry it. These methods will help remove any harmful microbes attached to the wood.

Once it is clean, you can use it in the Aquarium. You need to soak the wood in water for tannins to release. Driftwood not only lowers the water pH but also adds aesthetics to your Aquarium. Moreover, it adds a slightly brown tea colored effect to water, giving a more natural look to your fish tank.

6- Using Peat Moss

Another frequently used method for quick and effective pH drop is using peat moss. These are rich in tannins and can help drop pH to dangerously lower levels within no time. Thus, using peat moss accurately requires lots of experience, and beginners should avoid using peat moss for Aquarium.

Peat moss is a particularly strong acidifier and has abundant tannins, as tannins are yellow- orange. Thus, using peat moss will turn your Aquarium into a rusty color. A small amount of peat moss can do wonders and lowers the pH to the desired range.

The best way to use peat moss is to add it to the filter and let it slowly release tannins in the water. Another effective method is to use a filterable bag, add a small amount of peat moss, and hang it in the Aquarium.

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Be careful while using peat moss as it can cause excessive acidity in your tank and can even kill your fish in a split second. Thus, you should only use peat moss if you are 100% sure about its required amount and aware of all the precautionary measures to avoid dangerous outcomes.

7- Reverse Osmosis Units

Reverse osmosis units or ROs are an ingenious solution to carbonate hardening and mineral buildup in water. At places where there are excessive minerals or waste products in water, ROs help remove such harmful waste.

ROs work through a set of semi-permeable membranes designed to entrap heavy particles like Sulphur ions, metal ions, carbonates, and other toxic agents. The only freshwater is allowed to pass through the fine membrane. This way, there will be no toxic element in water, and pH will remain stable.

The only drawback with ROs is their price tags. They are not cost-friendly and thus become a nuisance for the fish keepers.

8- Using Catappa Leaves

Catappa leaves, or the Almond leaves (Terminalia Catappa), are another vital source of tannins and thus are beneficial in lowering the pH. Catappa leaves are rich sources of tannins, but they slowly release these agents with their decay.

You can put the leaves directly in the Aquarium or can also store the leaves inside the filter. Either way, it is equally beneficial. Catappa leaves can give your Aquarium a natural pond kind of look with its yellow-brown color. A handful of Catappa leaves is enough for a 70– 100-gallon aquarium. It can buffer the pH without harming the fish.

  • Reduce Water Aeration

Another practical and convenient method of reducing pH in the Aquarium is limiting the tank’s oxygen content. Out of all the gases, oxygen is considered neutral or slightly alkaline. Thus, decreasing the basic agent will quickly shift the pH toward the acidic side, leading to increased CO2 concentration.

This method is effective if done cautiously; if oxygen concentration drops to dangerously low levels, it might kill your fish.

10-  Stable pH is Better than Perfect pH

Last but not least, the prime focus should be to maintain stable conditions rather than striving for perfection. Once your fish acclimatized to certain water parameters, you should try to retain them for longer times.

Avoid any drastic changes in pH; a rapid increase or decrease in the pH level can put your fish in danger. One important thing to be kept in mind while adjusting pH is that 1 unit increase in pH has 10-fold effect and 2 unit increase in pH has 100 fold effect.

Thus, tryouts on 20-30% water are an excellent way, to begin with. Keep a close eye on your fish and keep monitoring the pH from time to time.


To wrap this all up, variation in pH is possible, and things can get out of hands sometimes, so you must know the effective method to bring them back to normal. Don’t overcrowd your Aquarium, don’t overfeed your fish, clean your Aquarium regularly, and keep checking the water parameters to avoid harming your fish.

I hope you will find the way that suits you the best in reducing alkalinity. Good luck with your Aquarium!

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