Hepper is reader-supported. When you buy via links on our site, we may earn an affiliate commission at no cost to you. Learn more.

How to Safely Lower pH in Your Aquarium: 4 Proven Methods

Lindsey Stanton Profile Picture

By Lindsey Stanton

PH checking solution in aquarium tank

Inviting a pet into your life has benefits that go beyond having a companion on the trail or an animal to listen to your woes about work and life. Fish are unique in this respect because you can help reduce stress and improve your well-being just by looking at them in the tank1!

There’s a reason that over 13 million households have an aquarium in their homes2.

A tank gives you a “window” view of your fish’s lives. It’s part of what makes maintaining a healthy aquatic environment so vital for both you and them. You see everything that goes on with them, and their behavior can offer valuable clues about any problems in the aquarium, including issues with water chemistry and pH.

Our guide goes over this vital element in relation to the health of your fish. We show you how to lower the pH to an optimal level, from simple to more complex ways to get the job done safely.


The Significance of pH for Your Fish

It’s essential to understand the context of pH in your fish’s world. After all, it’s the equivalent of the air we breathe. Just like for terrestrial organisms, stability is the key. Imagine the effects of air quality on human health to put it into perspective: Poor air quality can increase asthma attacks, reduce immunity, and increase the risk of heart disease and lung cancer.

The view from the piscine perspective is similar: Poor water quality can decrease the quality of life and increase the mortality rate of your fish.

The importance of pH varies with the species. Some fish thrive in lower pH levels, which translates into a more acidic environment. Conversely, a high pH means a more alkaline situation. The upshot is that it depends on the species’ habitat, with one caveat. It’s difficult to find wild-caught fish at your local pet store.

Most are captive-bred, which means that their water chemistry requirements aren’t necessarily that cut and dry. The relatively short generation times of aquarium fish mean that they can adapt quickly to these environments.

Goldfish swim in an aquarium_Val Krasn_shutterstock
Image Credit: Val Krasn, Shutterstock

Before You Start

While today’s aquarium fish are adaptable, there are still a few things that you must keep in mind when making any changes to your tank. For example, all aquarium fish require a stable environment. Any changes you make to the water chemistry must occur slowly to give the fish time to adapt to what’s happening in the tank.

Remember that changes in a pond, lake, stream, or sea will happen bit by bit. Therefore, fish are used to this pace of change in their lives. That’s your goal when lowering the pH in your aquarium. So, let’s start with the basics.

What Is pH?

Technically, pH is a measure of the amount of hydroxyl and free hydrogen ions in water. The liquid is either alkaline or acidic, based on which side of the scale it leans toward. The unique aspect of pH is that it’s a logarithmic scale. A change of 1 equals a 100-times difference in the pH.

PH runs from 1 to 14. Perhaps confusingly, the lower the pH, the more acidic it is, and the higher the pH, the more basic it is. That means several things for you as a pet owner. First, you must proceed with caution because a little change is a big change. Then, you must remember the stability factor. Fish don’t like change. They prefer the status quo.

That means you must take a direct approach when lowering the pH in your aquarium. Our guide suggests various methods, from minimal to more invasive, to get the job done.

Male hand holding PH tests in front of freshwater aquarium
Image By: M-Production, Shutterstock

Setting Baselines and Evaluating Effectiveness

You must start with a baseline to see what changes you are making to your tank’s pH. The pH can vary daily or weekly, depending on the population and species. We suggest monitoring every week. This measurement will reflect the average pH of your water based on modifications from feeding, fish, and the cleaning routine.

The 4 Methods to Lower pH in Aquariums

The best way to manipulate the pH is to create an easy segue from abnormal to normal. Fish can handle subtle changes, as these have the least chance of stressing them out. Some fish are more sensitive than others. They may have a lower acceptable pH range. Therefore, we recommend starting with ways that minimize the stress.

1. Decrease Aeration to Encourage Organic Chemicals

The nitrogen cycle is the recycling of waste products generated by the aquarium denizens. Oxygen and carbon dioxide are supporting actors. Beneficial bacteria convert waste from ammonia to nitrites to nitrates. The end product is a nutrient that plants can use.

Filtration speeds the process along to keep the pH at an optimal level. Otherwise, it can lower it. Simply slowing the aeration allows the pH to decrease without any other intervention. However, it’s a tightrope between optimal and dangerous levels.

aquarium tank with sponge filter
Image Credit: SritanaN, Shutterstock

2. Put Nature to Work

Many plants contain acidic compounds. Apples have malic acid, which gives them their distinctive taste. Likewise, wood has tannic acid. That’s one reason that winemakers use oak barrels to acquire the vanilla and spice flavors that they want to impart to wines. The acidity increases the aging ability of wines. Tanks use driftwood to accomplish the same purpose.

Another method involves peat. While it has the same effects, it’s quite messy. You can either use peat-treated water or peat contained in bags to minimize the waste that it generates.

3. Water Changes

Sometimes, you have to take a more proactive approach to lower the pH in your aquarium. These methods risk making drastic changes. We suggest trying the earlier options first. The underlying theme with these options is still minimizing anything that alters the status quo dramatically.

Conventional wisdom is to focus on the precise amount of change. Analyzing the water chemistry, including the pH, hardness, ammonia, nitrites, and nitrates will help give you a baseline. That’s assuming that the environment and its population stay the same. Any changes you make can disrupt the status quo.

We suggest starting with a 10% change once a week, followed by regular testing. Adjust the frequency and amount to keep everything stable. But there isn’t an overall set formula. Other factors also come into play, such as the aquarium size, filtration method, and feeding frequency. Testing the water is the best way to focus on the suitable water change frequency and amount.

man cleaning aquarium using magnetic fish tank cleaner
Image By: hedgehog94, Shutterstock

4. Last Resort: Additives

The last resort for lowering the pH is to use additives. The problem with these is that they can create drastic changes, which can stress out your fish. You only need to add a small amount to make a big variation. Some species can tolerate changes better than others. You can make it less critical by choosing species with similar environmental needs.

wave tropical divider

Final Thoughts About pH

The key to lowering the pH in your aquarium is understanding what the fish need and what can harm them. Changes in the status quo are red flags. Fish prefer and need a stable environment. That means you need to proceed cautiously with water chemistry changes. Otherwise, you risk stressing out the fish too much, too quickly. That puts them at a heightened risk of disease and parasite infestation. So, as long as you proceed slowly, you can drop the pH of your tank to the optimal level for your fish.

Featured Image Credit: finchfocus, Shutterstock

Related Articles

Further Reading

Vet Articles

Latest Vet Answers

The latest veterinarians' answers to questions from our database