How to Lower the pH in Your Fish Tank or Aquarium

Having an aquarium and keeping fish is one of the best ways to improve your home’s aesthetics. Keeping an aquarium running is also an excellent hobby, as long as you are okay with the amount of work this will involve.

Keeping all your fish satisfied and your aquarium in top shape may sound easy, but these are actually relatively difficult tasks that you will have to spend large amounts of time and (sometimes) small amounts of money for maintenance.

While your fishes’ health depends on many factors, one of the most important factors you need to monitor in your aquarium is its pH level. Today, we will provide more information on this measure and answer the following questions:

  • What is pH?

  • Why is pH important?

  • How can I control my tank water’s pH level?

Without any further ado, let us get started!

What is pH?

pH, simply put, is a logarithmic scale used to specify the acidity or basicity of a solution. The pH scale is easy to understand. It ranges from levels 0 to 14, with lower pH levels indicating higher acidity and higher levels indicating higher basicity or alkalinity (both terms that indicate the opposite of acidity).

Without turning this article into a chemistry lesson, a good way of looking at it is:

  • A solution with a pH level between 0 and 6.9 is acidic.

  • A pH level of 7 indicates neutrality, showing that a solution is neither a base nor an acid. Distilled water is one of the most common solutions you can find.

  • Finally, a pH level greater than 7 and less than 14 indicates that the solution is more alkaline.

The pH scale is logarithmic, which means that increasing the pH level by 1 is equivalent to changing acidity levels by 10 times the previous level.

Why is pH Important?

Why do so many aquarium owners focus so strongly on pH?

The answer to this lies in the fact that different types of fish require different pH levels to thrive. While fish will generally (not always) survive a little fluctuation in their water’s pH levels, massive changes and changes for long periods may lead to your fish dying.

Ideal pH Levels

Many new aquarium owners want to know what the perfect pH for their freshwater or saltwater tank is. Unfortunately, there’s no universal pH level that all fish will love. You will have to adjust the pH level in your aquarium to match your fish’s optimum range.

This is also a factor when buying new fish since you will need to confirm whether your new fish requires the same pH conditions as your existing pets.

Saltwater fish generally prefer environments that are more alkaline and will thrive in water with a pH level of 8 and above. Freshwater prefer lower levels of alkalinity and have an optimum pH range of between 5.5 and 7.5.

Keep in mind that these are general measurements and preferences. We recommend that you look up your fish breed’s preferred pH level for greater accuracy.

If you are going to be checking your aquarium’s pH levels regularly, you should know that pH levels typically fluctuate over time. In fact, you may even get different results from two measurements made on the same day.

Speaking of testing pH levels, you will need a water test kit to test your aquarium water. The API Test Kit is one of the best water test kits you can buy, and it also comes with a pH adjuster. The test kit comes in a variety of options, from solutions to add calcium, ammonia, nitrates, nitrites, and even copper into your aquarium water.

How can I control my tank water’s pH level?

And now we come to the meat of this article – how does anything we have said earlier translate into the real world? How can you actually change your tank’s pH level?

Today, we will cover a few methods you can use to adjust your aquarium’s pH level. We’ll cover a few natural methods and a few non-natural ones, so feel free to pick the one that appeals to you the most!

Before you jump to the methods below, we would like to give a disclaimer: most fish do not require exact pH levels for survival. If you know that your fish prefers a pH of 6.0 and your tank is at 6.4, you do not necessarily need to make any changes to your tank water.

However, if your fish are showing signs of ill health or distress or you are witnessing a trend where pH level has continuously been dropping, feel free to start trying out the techniques below.

1. Changing Water

The most basic of the techniques we will cover today, changing water is the simplest way of adjusting or resetting pH levels for your fish. If your fish prefer the pH of ordinary tap water, you will have to change out the water regularly to maintain that level.

pH drops naturally over time, but cleaning your aquarium by removing any waste or leftover food will reduce the rate at which this drop occurs.

2. Wood and Rocks

Adding specific types of rocks and wood is one of the best ways of reducing your tank’s pH levels. Rocks such as crushed or petrified coral and limestone will both lower your aquarium’s pH level.

You can also use pieces of driftwood and other organic material to lower your aquarium’s pH level. Driftwood creates a natural filter for water, but it has the disadvantage of potentially altering the color of your water.

If you do not want to discolor your water, many companies sell organic materials such as almond leaves or cholla wood that you can use to lower your tank’s pH without affecting the water’s color. Such products have the added advantage of decorative design and may make your tank look better.

Almond leaves are an excellent choice for any aquarium. These leaves confer several benefits to anyone who uses them in their aquarium. They improve fish health, have an anti-inflammatory effect on fish, and look excellent in your tank. While you may worry about hiding other additions to your tank, almond leaves add a touch of elegance and color to any aquarium.

3. Inorganic pH Adjusters

You can change your tank water’s pH level by using artificial pH adjusters. Fortunately, these products are all tested and proven safe for fish.

Most products like this will reduce your aquarium water’s pH level, such as the Fritz Aquatics pH lower and the API pH Down, the latter of which is a part of the API test kit we talked about earlier. Other products will neutralize your tank water’s pH levels. An example of these is the Seachem Neutral Regulator, which adjusts pH to 7.0 when added to a solution.

4. Reverse Osmosis

Reverse osmosis is a water purification technology that removes contaminants such as ions, molecules, and other large particles from water. Reverse osmosis is typically used in water purification plants because of how effective they are.

Reverse osmosis filters are also useful for fish because they remove harmful contaminants while allowing smaller ions to remain in the water.

The main drawback of reverse osmosis is its cost. A reverse osmosis system can cost you a significant amount of money when you buy it, but many buyers claim that spending on this technology gives you excellent value for your money.

If you are considering getting a reverse osmosis system, also keep in mind that RO systems are usually bulky and may be harder to install in small aquariums.


While getting into the world of aquariums and fishkeeping can be rewarding, it also involves a lot of learning and hard work. We hope that this article helped you understand pH and how adjusting it can improve your fishes’ health and wellbeing.

If you have any questions or think we have left anything out, let us know in the comments, and we will be glad to get back to you with any and all help you may need!

Leave a Reply

Scroll to Top