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Lowering pH in a fish tank

Aquariums can make a lovely addition to your home, both as a decorative piece and to have some beautiful fish to care for as pets. But aquariums require some careful maintenance. This is to ensure both the continuing health of your fish and the cleanliness of the tank.

One of the most important aspects of this maintenance is the pH level of the water in the aquarium.

What does pH mean?

The pH level of your tank water refers to the level of acidity or alkalinity of the water. A pH scale from 0-14 is used to determine whether the water is acidic or alkaline. For example, a neutral pH would be around 7. Anything below this and the water is considered acidic. Any higher than this and the water is considered alkaline.

Different types of tests, such as pH testing strips (also known as a litmus test), can be used to determine the pH level of water.

Why pH is important for aquariums

The pH level of your water can have a drastic impact on the health and behavior of your fish. Different types of fish thrive in different pH levels to stay healthy and happy. 

Some fish are also more sensitive to changes in pH levels than others. Once you understand the ideal pH range for your type of aquarium and the fish you have in it, the most important thing is to keep the level as stable as possible within that range.

How to know the correct pH for your fish tank

Saltwater tanks generally require a higher pH level than freshwater tanks, but it really comes down to the species that you’re housing within the aquarium. Take the time to research and understand the ideal pH level for your existing colony of fish, and take this into consideration before adding any other fish to the tank.

If you’re in doubt, consult a specialist veterinarian or an expert at your local pet store. Anyone who is selling aquarium fish should have a thorough understanding of the best water pH level for those fish.

Steps for lowering the pH of tank water

There are a couple of different methods of lowering the pH level in aquarium water. The most important thing is to test regularly and ensure the safety of your fish before making any changes. 

Step 1: Test the current pH level

The first thing to do is ensure that the pH levels of your tank water need to be lowered rather than raised. Your best bet is to get a pH monitor for aquariums. They are highly accurate and very quick and simple to use, especially as you’ll need to test the water regularly.

Compare the existing pH level against your ideal range. If it’s sitting within the range, you’ll just need to monitor closely and ensure it remains stable. If it’s a little high, or even sitting at the very upper level of your ideal range, it’s time to take steps to lower it.

Step 2: Add some natural pH lowering products


There are a few completely natural items that you can add to your aquarium to lower the pH levels. These items include pieces of driftwood, peat moss and cappata leaves. You can try all of them, but remember to go one at a time, and continuously test the pH level as you go.

Step 3: Deionize the water

reverse osmosis filter

Buying a special reverse osmosis filter can be expensive, but it’s a good way to lower pH levels and, more importantly, keep them stable over time. They’re particularly useful for reef aquariums and saltwater species of fish.

The filters remove any issues from your local water source, such as hard water, that may be impacting your ability to keep the pH levels low enough.

Step 4: Try some chemical pH adjusters

If all else fails, you can try some chemical pH adjusters for aquariums. Typically, you only need to add a couple of drops of pH adjusters as needed to maintain an ideal and stable level for your fish. However, they should be used with caution, as they can cause a sudden change in pH that can be harmful to your fish.

What you need to buy for lowering the pH in an aquarium

API pH Down pH Adjuster

API pH Down pH Adjuster

This treatment is easy to use and can be used to lower the pH of both fresh and saltwater tanks. It also works fast, which is ideal if your pH levels have gotten dangerously high.

Where to buy: Sold by Amazon, Chewy and Petsmart

Fluval Aquatic Peat Granules

Fluval Aquatic Peat Granules

These peat granules can be added to the filter of your aquarium to naturally lower the pH levels of your aquarium. However, it’s only suitable for use in freshwater aquariums.

Where to buy: Sold by Amazon and Petsmart


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Lauren Farrell writes for BestReviews. BestReviews has helped millions of consumers simplify their purchasing decisions, saving them time and money.

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