How to Lower pH in Aquarium? Probable Causes & Helpful Tips Explained!

fish tank

Fish make great pets and are essentially popular for their minimal upkeep. But who owns an aquarium knows the patience and perseverance required for its maintenance.

Taking care of an aquarium can be a little tricky, particularly when it comes to maintaining a certain level of pH, whether it’s a freshwater aquarium or saltwater fish tanks.

No matter the species, any sort of fish will suffer from a drastic increase in aquarium pH level as the environment no longer remains livable.

Therefore, it’s a crucial skill that every aquarium keeper needs to master to ensure a healthy lifestyle for the majestic water creatures.

This article will be your guide to natural and commercial methods to lower the alarmingly high pH level in the tank. Ready to become an expert? Dwell right in!

What Is pH in Aquariums?

 pH for Freshwater

Rings any bell from the chemistry class in high school? Time to revisit that unpleasant memory lane.

pH refers to the ‘potential of hydrogen.’ It is a scale to quantitatively measure the acidity or alkalinity of an aqueous or other liquid solution. The more the hydrogen ions concentration, the more acidic a solution is.

The range of the pH scale falls between 0-14. For instance, pure water has a pH of 7, which is neither acidic nor basic; it is a neutral pH. If the pH exceeds 7, it is called alkaline or basic. pH less than 7, on the other hand, is known as acidic.
The concentration of bicarbonates, carbon dioxide, and carbonates act as active agents to lower or high the pH in water. Both too acidic water and too alkaline water in the tank are detrimental to fish.

What Is the “Ideal” pH for Freshwater Aquariums?

The range between 6.8 and 7.8 is largely considered suitable for freshwater aquariums, tropical fish, or fish species.

However, pH fluctuation above or below this range can seriously impair aquatic life’s ability to function normally. When the pH is below 6.5, water doesn’t have the buffering capacity to prevent pH levels from decreasing even further.

The good thing is that fish are adaptable organisms. A slight variation in the fish tank’s pH level occurs throughout the day and isn’t particularly concerning.

What Causes High pH in Aquariums?

Monitering the pH in the aquarium is not enough. To properly address the pH imbalance issue, you must be aware of all the potential contributing elements resulting in high pH levels.

What Is pH in Aquariums?

Directly adding tap water, which probably contains metals and alkaline substances, can raise the pH level. That’s why it’s crucial to measure water’s pH before adding it to the aquarium.

High pH levels can also result from certain substrates, gravel, or sand( such as limestone).

If you add untreated water or the canister filter inside the tank is ineffective or malfunctioning, the toxicity inside the fish tank builds up and increases pH.

If you have too many aquatic plants, they can feed on the majority of the carbon dioxide. This decline in CO2 makes the pH rise in fish tanks.

Baking soda is an effective agent aquarists use to manage pH levels in the fish water tank; if added too much, it can cause an increase in pH.

Baking soda is an effective agent aquarists use to manage pH levels in the fish water tank; if added too much, it can cause an increase in pH.

How Often Should You Test pH in an Aquarium?

Testing the aquarium pH is vital to ensure an optimal living environment for the water creatures.

You should test the pH of the water at least once a month. Ideally, it should be every two weeks. If you notice an unusual pattern in the readings, keep the record and find a permanent solution immediately.

The timing of the pH testing can affect the result readings. Make sure the testing timings are the same as you previously scheduled them. The best time to perform a pH test would be daytime for accurate results.

Optimal pH levels for fish can vary depending on the species. It’s wise to ask the shop/expert what pH level your fish will thrive on and then maintain that reading.

Also, if there’s been a sudden fish death incident in the aquarium, take it as an indicator to test the pH.

When Is It Necessary To Lower the pH in Aquariums?

Even if you don’t check the pH directly, there will be visible signs implying the pH level is higher than necessary.

First, if you notice rapid algae growth, it likely means the alkalinity of the water tank is high. Algae growth skyrockets in high pH, soaking up the oxygen levels and blocking the sunlight for the aquatic plants at the bottom bed.

It turns the water cloudy and makes it difficult for the aqua creatures to survive. Try bringing the pH down gradually. The sudden introduction of pH-lowering agents brings more harm than good. So, do it over the course of weeks, not abruptly.

Secondly, if your fish has been hyperactive out of the blue, it is possible it might be having troubling breathing due to high pH.

Or if you notice them scratching their fin against the rock miserably, they might suffer from ich, caused by higher pH inside the water tank.

If any of the above signs catch your attention, that’s when you know it’s necessary to reduce pH.

Tools To Monitor the pH in Your Aquarium

You will have to buy testing kits to monitor ph. Thankfully, pH testing kits are available at an affordable price and offer accurate results. You can choose from multiple options; let’s discuss a few.

aquarium pH

pH Water Test Kits

The aquarium test kit is the easiest and simplest way to test the pH in your aquarium. All you need to do is take the sample of the fish aquarium water in a test tube( or whatever is convenient) and add the testing solution. Then match the water’s color with the given card guide.You can find these kits for freshwater, saltwater aquarium, or outdoor ponds.

pH test paper, also called litmus paper, is another cheap and quick way to measure pH. Simply dip the strip in your tank and wait for it dry. The color will indicate how acidic or basic your fish tank water is.

Digital pH meter is the most accurate but a little bank-breaking way to test pH. Although, it is acquired mostly by fish breeders who maintain pH levels on a high scale. So, you are good to go with the affordable options.

Recommended Techniques for Lowering pH in Aquariums

Below are some ways of adjusting pH to keep water’s pH stable.

how to lower ph in fish tank

Chemical Solutions

Chemical solutions are efficient solutions to reach a balanced pH reading thanks to their swift results. There are a lot of choices available out there.

One of the options you can go for is to get a gallon of muriatic acid or phosphoric acid, whichever is easily accessible. Muriatic acid is more commonly available; you can easily get it from a food supply shop or home depot at a reasonable price.

The next step will be to get a garbage pail. It should have a holding capacity of something between 25 to 35 gallons; the bigger, the better. Now, add muriatic acid with its bottle lid in the water and let it sit for three days.

Check the pH again. The amount of muriatic acid you add can carry with your needs or the pH reading you’re trying to achieve



Adding driftwood to the fish tank is also an eminent natural hack to keep the water chemistry under control. The good thing about driftwood is that you can safely lower pH and simultaneously add to the aquarium’s aesthetics.

Your fish will love the vibe! They will get to play hide-and-seek or buy themselves a little privacy. Although prevent overcrowding the aquarium, leave plenty of space for your fish to swim comfortably.

Make sure you get aquarium-safe driftwood, as its other variations can prove to be more toxic than beneficial. Place the driftwood at the bottom, followed by refilling the tank. It will gradually lead to a low pH in the aquarium.

Peat Moss

 aquarists and hobbyists.

Adding peat moss is a common and highly recommended method by aquarists and hobbyists. It is an excellent way to naturally lower the pH level in aquarium water. The acidity of peat moss comes from its richness in tannins, which effectively aids in bringing the pH level down and softening the aquarium water.

The term ” tinted water” is often associated with the peat moss method as it has the tendency to turn the water yellow. In order to prevent the yellowish tint, we recommend soaking before introducing peat moss to the aquarium.

Remember, natural methods usually take longer, and the result might not be abrupt. And the amount of peat moss you add also determines the time it will take to lower the pH.

There’s no right amount. The correct technique is to add peat moss and check the pH level. Keep repeating till the pH levels lower.

You can add it as a substrate, hang it in a stocking, or add it to the water filtration system. Or you can soak the peat moss and add that water into the fish tank.

Catappa Leave

Catappa leaves, also called Indian almond leaves, bring tremendous benefits to the aquarium and fish community.

First, these leaves help lower ph levels by discharging tannins into the tank water. But it doesn’t end here. It is scientifically proven that Catappa leaves combat and protect the fish tank water from bacterial and fungal infections.

Did we mention how these leaves are a fabulous feast for the shrimps? Shrimps do deserve a little treat in return for keeping the aquarium food waste and algae-free.

You can add the Catappa leaves directly or sprinkle the crumbles. Don’t go overboard; you don’t want the aquatic creatures to experience a pH shock.

Keep adding gradually, and monitor the ph level alongside.

CO2 Reactors

co2 reactor in plants in aquarisum

Getting a CO2 reactor will especially prove to be beneficial if your aquarium has live plants in abundance, as their growth boosts in CO2.

CO2 reactors act as a constant source of carbon dioxide emission in the planted aquariums. The mildly acidic nature of carbon dioxide buffers the alkalinity and lowers the pH.

Water Changes

how to  lower aquarium ph

Partial water changes in the fish tank are something you should normally do to ensure the well-being of water-based creatures. It is also an effective way to balance ph levels.

Water changes enable you to get rid of ph imbalance contributors/agents, harmful components like ammonia, and unwanted minerals. This way overall cleanliness of the tank is maintained, and the organic waste accumulated over time is also wiped off significantly.

Now, changing all the water inside the fish tank is not feasible. Therefore, swapping off 20-30 % of the water will do the job.

It’s a good tactic for pH equilibrium but can prove to be a little less effective if the root cause of higher ph is something else. Make sure you check the ph of the water before adding it and that its temperature reading matches the aquarium.

Don’t add the tap water directly; it is equivalent to contaminating. Use de-chlorinator. It’s best to manually clean aquarium plants and sand/substrate (using a siphon or whichever method you prefer) beforehand.

These regular water changes will tackle the ph disturbance up to a large extent. Besides, that’s how to get crystal clear fish tank water; frequent cleaning, water changes, and pH balance.

Reverse Osmosis Units

ph in aquarium

Reverse osmosis units refer to a water filtration/purification method used to extract contaminants and unwanted molecules with the help of a semi-permeable membrane. Now, how do you lower the pH level of an aquarium’s water using this method?

For that, you need to buy a reverse osmosis unit. Done buying? Take every part out of the packaging. The unit will likely comprise two carbon filters to prevent chlorine and chloramine from destroying the membrane. The membrane that will do the cleaning work will be blue in color.

Done unboxing? Time to install, which is pretty simple. Take the membrane and slide it right into the housing on the top of the unit, ensuring the black rubber seal faces outside. Then plug the opening as tight as you possibly can. The membrane part is done!

One of the chambers will contain the carbon filter, while the sediment filter will occupy the other one. Now, the performance of the RO water unit depends heavily on the membrane quality and water flow restrictor.

Most membranes have 100 gallons of soft water production per day. In your case, if you have an average-sized tank, it will take you 8 to 12 hours.

Reverse osmosis is a great way to combat pH imbalance as it effectively filters the water removing heavy ions like sulfur and every kind of toxins/harmful chemical.

There’s one drawback of this method. It has the tendency to filter out essential compounds/nutrients too.

Dangers of High pH in Aquariums

Everything functions well in the state of equilibrium. The same goes for an aquarium. When the pH level in most aquariums rises above the normal range, it can be harmful in many ways.

The slime coat fish use to keep the parasites/bacteria away gets impaired in high alkalinity, making fish more prone to illnesses and parasite attacks. As the protective layer is damaged, fish can get painful chemical burns on the scale, eyes, and gills.

Moreover, ammonia from fish waste/food becomes toxic in high-pH solutions. Ammonia poisoning can cause distress and internal organ damage and can even result in the death of your fish.

High pH levels also impact plant life in an aquarium. For instance, algae start to go rapidly. And when the algae boom comes to an end( it can’t sustain for longer), it will release nitrates, ammonia, and other harmful bacteria into the water upon decomposing. And that is very dangerous for your fish.


Having an aquarium undoubtedly is a treat to the eyes. It not only adds life to a space but also brings calmness and joy. It’s a great responsibility, too. If not taken care of seriously can result in the fatality of your water friends.

Monitor the pH level frequently and take action if necessary. Always keep a keen eye on the behavioral pattern of your fish.

Hopefully, this article helped. Best of luck!

Cody Mitchell
Cody Mitchell is a pet lover and a passionate pet writer. He has worked as a professional writer for over 6 years, with a focus on creating compelling content for pet-related brands. His work has been featured in major publications. When he's not writing, Cody can be found playing with his two dogs (a labradoodle and a cocker spaniel) or cuddling his cat.

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