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How to Lower pH in Aquarium (Causes & Quick Fix)

How to Lower pH in Aquarium (Causes & Quick Fix)

Having a fish tank in your home or office can be a great addition. Watching the fish swim around can provide excitement for you, your kids and visitors. The last thing you want to see is to wake up to see your fish floating dead in the tank. This is the reason why it pays to monitor the pH and other factors that can affect the health of your fish.

It is important to keep the pH levels constant, regardless of the type of fish you have in your tank. In most cases, pH levels must be kept low, but not too low to become too acidic for the fish to handle.

Reducing pH Levels Naturally in Aquarium

You don’t have to wait until the water in your fish tank turns alkaline before you conduct a test. Test for alkalinity must be done every couple of days. You need to return the natural ecosystem in the aquarium water slowly into its balance.

One of the purposes of reducing the high pH levels in your fish tank is to boost aeration. Aeration will add and increase the flow of Carbon dioxide in the water inside the aquarium. Adding some Vinegar slowly into the alkaline water can equally help neutralize the alkalinity steadily, in a natural way. Perhaps, the introduction of new plants in the aquarium is the best natural way to reduce alkalinity naturally.

The pH Levels in Fish Tank and their Importance

The pH levels of any aquarium must be optimally maintained to avoid the catastrophic side effects of extremely high Ph. The pH inside the fish thank is important because it determines how much Oxygen your fish is getting inside the water in order to thrive. Lowering pH means more Oxygen will be available to the fish and higher pH means less Oxygen will be available.

Most fish tanks will perform well at a pH of between 5.5 and 8. If your fish seem to have depleted energy, then you should consider measuring the pH and lower it if it is getting too high.

A measurement of 0-6.9 pH is regarded as acidic, and a pH of 7.1 to 14 is regarded as alkaline. Aquarium fishes will thrive at a pH closer to 7, which is neutral. When an aquarium tank has a pH higher than 7.5, it is strongly alkaline and poses a serious threat to the fish and its habitat.

If your fish is showing the unusual slowdown in activity or some illnesses, then you must check the pH of the tank. When the pH levels are too high in your aquarium, your fish may suffer from symptoms of alkalosis. Symptoms of alkalosis may include; unusual excitement and swimming haphazardly (  irregular patterns.

In extremely high pH of 9 or higher, some fishes may try to jump out of the tank or scratch their bodies against stones or rocks inside the aquarium. You may also notice the fins of the fish spread wider than usual, or the gills may start to secrete mucus.

Your aquarium will likely show some signs of high pH in most cases. An increase in the growth of green algae in your aquarium is a sign of high alkalinity. These green algae may grow more and quickly on the walls of the aquarium and ornaments inside the tank.

High pH levels will sharply increase the growth of algae and slime in tanks. Plants and other fixtures in the aquarium may become coated with green algae when high pH issues are not resolved on time.

Just before you put anything into the fish tank, take a pause and consider the possibility of that thing raising the pH sharply. Most fish tank owners don’t bother to check the likelihood of pH variations that are caused by food particles and other components.

Fortunately, pH fluctuations occur gradually inside the fish tank, hence it is possible to avert danger before the pH change gets out of control. Changing the fish tank water partially, perhaps is one of the best possible ways to avoid catastrophic dangers of high pH. Changing at least 10% of the water in the tank daily perhaps can save the life of your fish from the negative effects of high pH.

What Causes high pH in Aquarium?

The cause of high pH in Aquarium is carbon dioxide depletion. Adding your regular tap water into your aquarium can cause a very sharp increase in the pH level of the aquarium. Secondly, the addition of alkalinity supplements can also trigger a sharp increase in pH levels. Even the placement of your hand or the fish bag from the store can increase pH levels in the tank.

Even regular foods added into the tank can cause a sudden spark in the alkalinity levels in the tank. The depletion of natural aquarium plant may cause depletion in the Carbon dioxide levels in the tank and that can increase pH levels steadily. It is quite important to maintain natural plants inside your aquarium to ensure steady CO2 supply.

pH in Aquarium

The addition of different fish food into the tank may cause a sharp increase in alkalinity. Similarly, placing fish decoration in the fish tank can also cause a slight increase in alkalinity. The waste materials from your fish (including the excreted substances) can increase pH levels. It is important to deploy an effective filtration system into the tank to remove waste materials released by the fish.

When you add untreated water from ground sources such as boreholes into your tank, it can quickly increase pH levels. Rainwater borehole water, water from streams, and ponds are extremely high in acidic or alkaline levels, hence they must not be added into the tank, untreated.

Will Plants Lower pH in an Aquarium?

Plants can either increase or reduce pH in an aquarium in different ways, it all depends on how you control their activities. While Carbon Dioxide will reduce the pH of water in a tank, Oxygen has no effect on pH. For this reason, plants in the tank will absorb more Carbon Dioxide thus eliminating it from water and causing a steady rise in the pH.

The elimination of carbon dioxide from water has a small but steady effect on pH levels. Aside from Carbon dioxide, there are several other compounds that plants can metabolize, and these will have effects on pH levels.

Plants, for instance, can absorb ammonia alongside other Nitrogenous substances. These Nitrogenous substances can trigger a number of biological processes that create free Hydrogen Ions that will lower pH as opposed to increasing it.

By absorbing more Nitrogenous substances from water, more hydrogen ions will be released by plants into the water, to lower pH. Plant species such as Egeria are known to be some of the best water plants you should add to your aquarium. Egeria plants will absorb other Ions such as Calcium which lowers buffering capacities in water to reduce pH levels.

Though dead plants may lower pH in your fish tank it is not advisable to promote such. Dead plants will disintegrate and rot inside the tank, this will cause a sharp release of ammonia and other Nitrogenous substances into the water, causing lowering of pH. Allowing dead plants to rot inside water is not good for your fish. It is important to remove dead plants and change the water in the aquarium as soon as you discover dead plants.

While plants can either increase or lower the pH in the aquarium, the high pH in the tank can also affect the living plants in some ways. Just like fish, plants can adapt quickly to their local environment.

Species of plants, including the Amazon and Sword plant, will prefer the slightly acidic water inside the tank. Egeria species, on the other hand, can only adapt to slightly high alkaline water and not lowered pH. It is important for you to choose your aquarium plants carefully.

Can High pH Kill Fish?

Your Aquarium fish will start behaving unusually when the pH level is unusually too high. In extreme cases of high pH, you may notice your fish becoming sluggish, and breathing may become extremely difficult.

Increase pH levels in the aquarium may lead to a condition called “Ick” or “Ich” in fish. This disease can lead to the death of your fish if not treated on time.

It is easy to spot the signs of Ick on your fish, you will notice the development of tiny white spots spread all over the body. Infected aquarium fish will become lethargic, scratching its body against the aquarium wall. You may notice some bloody streaks on the fins of the fish.

Natural Ways to Lower pH in Your Fish Tank

Most fishes will perform better in lowered pH but the water must not be allowed to become too acidic to avoid an adverse effect on such fishes. In order to lower the pH level in your aquarium, you should consider adding natural stuff such as almond leaves, driftwood, and peat moss.

The use of Osmosis filter should also be considered as a natural way of lowering pH because it contains no chemical substances. The use of Osmosis filters for lowering pH is considered a viable long-term approach to maintaining a cleaner and well-balanced pH.

Generally, regular cleaning of the fish tank, especially with changing of water, can help protect your fish from high pH. The addition of natural substances like driftwood is equally important for a quick lowering effect of pH.

Reduce pH Levels in Your fish tank with Natural Driftwood

Add 1 or 2 pieces of Driftwood inside the aquarium at a time. The driftwood will act as a natural filter for the tank. Driftwood has no preservatives, dyes or any other chemical and 2 pieces are small enough to fit into small, medium and large aquariums.

Driftwood Fish Tank

Avoid manufactured driftwoods, they may contain some chemicals. It is also important that you boil the driftwood before adding it into the tank. Adding driftwood into the tank without boiling it may cause coloration of the water. Alternatively, you may want to soak the driftwood in clean water for about 10 days if you are not boiling it.

You can leave the driftwood inside your tank for several months or years and allow it to filter the water naturally.

Reduce pH Levels in Fish Tank with Natural Peat Moss

Alternatively, you can also make use of the natural peat moss to lower the pH levels in your fish tank. You need to spare some time for preparing this natural substance before adding it unto your aquarium. You can get the peat moss in the local pet store but make sure it is 100% organic and designed for use in fish tanks.

Make sure you soak the peat moss for about 4 days inside clean water for about 4 days before adding a handful into your aquarium. Soaking for some days before use will prevent the moss from turning the tank water into brown or yellow.

When placing the peat moss in the aquarium, make sure you use a filter bag to ensure that the moss doesn’t float. You should add the peat moss in small quantities inside the bag in order to lower the pH slowly and not abruptly.

You may also place your peat moss inside a filter in the tank, instead of the filter bag. You need to watch the lowering of the pH carefully as too much peat moss may cause the pH to drop below 4.0. A pH of 4 or lower is too dangerous for the survival of the fish, hence it must be added slowly. Make sure the peat moss is replaced every 6 months, as they get old and damaged.

Reduce pH Levels with the Natural Almond Leaves

You may also consider the use of Almond leaves to lower the pH of your aquarium. Almond leaves will not only lower pH levels, but they can also reduce the risks of certain diseases because of their anti-inflammatory properties. Almond leaves can provide a natural hiding spot for your fish, and they look aesthetically appealing inside the tank.

You can find good almond leaves at your local pet store and they are usually packaged dry inside strips. Just like the peat moss and Driftwood, you should soak your Almond leaves inside fresh and clean water for about 24 hours before placing them inside the tank. Soaking your Almond leaves inside water will help remove tannins that will likely turn your tank water yellow.

Almond leaves must be spread at the bottom of your tank after soaking. Almond leaves can provide some ground covering for your fish, especially when the tank is placed inside the sun. You need to replace the almond leaves every 6 months when they start to look ragged.

Cleaning and Maintaining Your Aquarium

Regular cleaning and maintenance of the fish tank must be considered as part of the natural ways of maintaining low pH. Experts recommend that you should clean your aquarium every 2 weeks. Regular cleaning will help prevent the buildup of Ammonia in the system, a situation that may cause extremely high pH.

During cleaning, you need to ensure that all green algae on the walls of the tank are scraped off with the use of the proper scraper. You need to replace about 20% of the water in the tank with fresh, clean one, at a time. It is quite unsafe to replace all the water at the same time. You can make use of a recommended siphon to remove the gunk on the surface of the gravel and all tank decorations.

You need to clean as many parts of the gravel as you can, in order to remove waste materials deposited by the fish. All food particles or leftovers must also be removed from the tank during cleaning.  You don’t have to remove your fish or any of the tank’s components while you clean the tank. Removal of the fish during cleaning may expose her to some kinds of sicknesses or death.

If you have a filter inside your fish tank, you need to check if it is working properly. Make sure it is not dirty or clogged, if not you need to remove it completely and clean it. You don’t have to clean the filter each time you clean the tank, most filters don’t get clogged or dirty too frequently.

To clean the filter, simply remove the component and then rinse them below running cool water to eliminate the sticky gunk and debris. Pay attention to the instructions written on the filter in order to achieve proper cleaning of the sponge, cartridge and carbon packets.

Other Cleaning Tips and Ideas for the Fish Tank

If you have some time to spare, you may want to replace about 10% of aquarium water, once in a day to keep pH levels low. You can do this change daily or once in every 2-3 days depending on how much time you have. Make use of a siphon to remove the water and then add new immediately.

The siphon method is the most convenient way to remove water from a fish tank without breaking any accessory or injuring the fish. Using bowls or any other method may cause the water to spill, and may even cause damage to the aquarium or any of its components.

If you have to wait for 5 days or more than perform a partial water change then you can replace up to 40% of the water at a time.

Perform a pH test on your aquarium water once a week. Testing the pH of the water once a week can help you detect average pH changes in 1 month- You can do this by calculating the average. You need to understand the pH requirement for your fish, and testing the pH once in a week will ensure that the optimal range is maintained.

Different fish species do possess different tolerance levels for pH variations. Some can thrive at low acidic levels of up to 4 and some may thrive at alkaline pH levels of up to 9. Subjecting your fish to extremely low or high pH levels for a long time can be a disaster.

Everything you add into the fish tank must not trigger a sharp increase or lower of pH. If you are adding fish food, do it slowly at intervals to prevent rapid lowering or increase in pH. Rapid pH changes are the leading cause of sicknesses and other issues that affect fishes in the aquarium.

If your fish tank is not covered, other pets like cats and dogs may go there occasionally to drink the water. This may cause food poisoning to your pet. Aquariums must be covered especially if they are in direct contact with sun rays, and to prevent foreign objects from entering.

Avoid the use of substances such as Vinegar because they are acidic. Vinegar may be too acidic and too strong for your fish, in some cases; it may cause the death of the animal. Vinegar can actually reduce the pH of water in the fish tank but it should be avoided by all means.

It is important that you prevent issues relating to water sources and filter problems. Do not make use of public water sources such as boreholes to fill your aquarium. Boreholes are notorious for providing high alkaline water, hence they can be detrimental to the survival of your fish.

If your household relies on borehole then the water being supplied must be chlorinated as part of its treatment.  Borehole water may also be a source of bacteria and fungal diseases, and that is another reason it must be treated.


Maintaining a healthy aquarium should be a collective responsibility of an entire household. Make sure you teach your partner and kids on how to change the water partly if you are not around. Also, pay attention to any component of the aquarium that is becoming rusty, weak or less functional.