How to lower ph in aquarium practical ways to adjust fish tank phLower pH in aquarium rapidly by adding vinegar to your tank water. Even though its effects are temporary, it gets the job done until you can find out what is causing low ph levels in your tank. It would immediately kick-start an ionization process causing the pH levels to begin to reduce. Keep reading to learn other ways to increase the pH in your fish tank.

How To Lower pH in Aquarium

If the pH in your aquarium is too high, here are some ways to safely lower it, so it reaches the optimal level for your fish. All methods are effective, but you are sure to monitor your pH levels after applying them.

1. Perform Regular Partial Water Change

You can naturally lower pH in aquarium by performing regular partial water changes. You see, the fish waste and leftover decayed food produce ammonia. High ammonia levels, in turn, led to elevated pH in your tank. Hence, getting rid of these ammonia sources would naturally lower the pH.

Furthermore, one would think that larger tanks require fewer water changes. However, this may be true if the aquarium has few fish producing less waste. Hence, study the tank and create a routine that keeps the ammonia content minimal. Note to get rid of debris and algae from the gravel and decorations in the aquarium.

2. Change Your Tank Filter

If your tank pH is too high, it may be time to change your filter. For instance, if you get a filter that is ideal for a five-gallon tank and install it in a 55-gallon aquarium. An inefficient filter would not sufficiently clean your aquarium water. Also, a dirty old filter would not suffice.

Still, if you decide to clean the filter, do not get rid of the sludge. This is because you may lose the beneficial bacteria growing in it. That is why we recommend only rinsing out the filter with water.

3. Add Peat Moss

Adding peat moss would naturally lower pH in fish tank. It is readily available in the form of pellets and chinks from pet stores. You may add them to your aquarium in various ways; one technique is by adding them to your filter. Although you can add the leaves to different tank areas, they are likely to float in the water.

Hence the filter is the best place to drop the peat moss leaves. Also, the leaves slightly discolor the water, turning it into a yellowish hue which can be uncomfortable for the fish. So, you should soak the peat moss in a separate container for a few days before putting it in the tank. Also, it is important you put in the right quantity of peat moss, or it could turn the water soft.

4. Add Driftwood to the Tank.

To lower pH level in fish tank, add in some driftwood. In the wild, driftwood can be naturally found in streams and rivers. So, putting them in the tank would simulate the fish’s natural habitat conditions. You can add one or two pieces of driftwood to filter your tank water. They release tannin, which gradually lowers the elevated pH in the aquarium.

However, like the peat moss, the driftwood gives off dark coloration, which changes the color of the water. But, the driftwood would not release contaminant that pollutes the tank. So, the sudden color change cannot harm your fish.

5. Add Indian Almond Leaves (Catappa)

Lowering pH in aquarium is pretty easy with the Indian almond leaves. You need to add them to your tank, and it will gradually reduce the pH. The leaves contain a component that would naturally reduce water pH. They are an aesthetically fascinating technique, and they help retain the pH levels at their optimal concentration.

Adding Catappa to a fish tank is safe. The cluster of almond leaves can serve as a hiding spot for small or shy fish. They also have healing properties that tackle certain fish diseases. Furthermore, they have antioxidant and anti-inflammatory properties, and they give a rejuvenating look to the tank. However, soak the leaves to remove the color before putting them in the tank.

6. Reverse Osmosis

You can lower aquarium pH using the reverse osmosis method. During RO, ions and molecules are extracted, making the water cleaner. Also, using a partial semi-permeable filter completely removes all contaminants in the tank. The filter allows small ions to flow but blocks off harmful heavy ones.

This method is expensive but effective in lowering pH in fish tanks. You would, however, need to replace your RO filter often. Furthermore, the filter is very big, so is more suited for large fish tanks.

7. Decrease Aeration in the Aquarium

You can lower pH in freshwater aquarium by applying the fundamental method of reducing your tank aeration. Carbon dioxide will increase when you reduce oxygen levels, leading to lower ph. The technique is quite tricky because your fish needs oxygen to survive. However, it is cost-effective and easy to implement but be careful to monitor the oxygen level as it could lead to fatality.

8. Add Carbon Dioxide to Your Tank To Reduce pH.

As mentioned earlier, increased carbon dioxide would reduce pH in aquarium. This method is similar to the oxygen reduction technique, but in this case, you add carbon dioxide to your aquarium.

You can do this by triggering a gaseous exchange. Use an air stone to agitate the tank water surface, and this would draw oxygen from the air into the water, thereby pushing carbon dioxide in the water into the air. This carbon dioxide reduction causes pH to increase.

9. Use Vinegar to Lower pH in Your Aquarium.

Add in some vinegar to help lower your tank pH level. But please note that this is a temporary fix and should not be used regularly. However, the vinegar would trigger an ionization process that immediately affects your tank’s water. Nonetheless, the whole process of reducing the pH takes some hours to finalize and work properly.

10. Use Chemical Additives

Many chemical additives would lower your tank pH, but they are not a permanent fix. You would have to continue adding them into your aquarium to keep the pH level low.

Causes of pH Shock

  • Large water changes when the old water in the tank has a wide difference in pH from the new one
  • Excessive CO2 and low KH of less than 4dkh can cause pH shock
  • Too much chemical additive
  • Transporting a fish for longer than three hours in a bag can cause a rapid pH shift when the trapped gases in the water are suddenly released

Please note that different fish react to sudden pH changes differently. Some are more tolerant than others.

– Effects of pH Shock on Fish

Ph shock causes majorly negative effects on fish. Here are a few of them.

  • The fish becomes lethargic
  • It loses appetite
  • Its dorsal fin would drop
  • The fish would hardly move around in the tank
  • Some fish would have slimy bodies that appear like an off-white color
  • After some days, the fish would die if the environment remains extreme

What Causes My Tank pH Level To Become So High

Here are some reasons why your tank pH is high:

  • Irregular water change
  • Excessive dissolved baking soda
  • Excessive oxygenation
  • Presence of Mineral Traces in the Water Source
  • Presence of Certain Substrate, Rocks, or Shells

1. Irregular Water Changes

If you do not perform regular partial water changes, the pH in your tank will drop over time. You should make regular small water changes over 24 hours than one large one. This would prevent the pH level from changing quickly and shocking your fish. Also, you have to diligently clean your tank to get rid of leftover food and fish waste.

2. Presence of Mineral Traces In the Water Source

Your tank would have high pH levels when the direct tank water source like your tap water is tainted with mineral traces like high phosphate and silicate levels. In this case, it will carbonate when you add it into your tank and raise the pH level to 7.0 and above.

3. Presence of Certain Substrate, Rocks, or Shells

Some substrate types or rocks and shells can cause your pH to remain high. An example is the common crushed coral substrate that African cichlid fishkeepers use. Also, some rocks and decorations contain trace amounts of limestones and crushed corals. So, if you must use them, use them in reasonable quantities, or they would cause a spike in pH levels.

4. Excessive Oxygenation

If you have an air stone and a powerful filter head, they may be the reason for the high pH levels. Hence, adjust the filter so the oxygen concentration in the tank would be minimal yet enough for the fish to survive.

5. Excessive Dissolved Baking Soda

Fish keepers regularly put baking soda on their tanks to reduce the pH levels. But, excessive amounts of baking soda can cause the pH to be high, thereby creating an unhealthy environment for the fish. If you add baking soda, one teaspoon to five gallons of water is fair. Also, dissolve the baking soda with some tank water first before adding it to the aquarium.


1. How Does Low pH Affect Fish in a Tank?

When the pH in a tank falls below 6.0, the nitrifying bacteria begin to die off.  Thus the toxic ammonia and nitrites would spike up, which would lead to fish death. Other effects of low pH in an aquarium include:

– Restlessness

The fish would seem irritated. You will observe it jumping and shimmying around the tank. It would show that it is uncomfortable.

– Breathing at the Water’s Surface

The fish would be seen breathing at the surface of the water. It would exhibit a rapid gill movement and struggle to breathe well.

– Fish Appear Pale or Dark

In some cases, the fish’s vibrant coloration would seem dull. It would look darker and pale.

– Flicking Against Objects

In extreme cases, the fish would begin flicking against objects, which can be quite dangerous. This is because it can hit itself against a sharp object causing an injury.

2. How To Prevent the Driftwood From Discoloring Your Tank Water

Thoroughly wash the chunk of driftwood until the color of the released pigment becomes lighter. Also, you should boil the driftwood to kill off any harmful fungi in it. It would also inhibit algae from growing on it.

3. Are Chemical Additives a Safe Method for Lowering pH in an Aquarium

No, chemical additives are not safe for lowering tank pH. This is because they can rapidly drop the pH levels in an aquarium, leaving the fish no time to adjust to change; hence, killing the fish. So we recommend a natural method as they gradually alter the pH of the aquarium.

4. What Happens When Aquarium pH Lowers or Increases Rapidly

If the pH in your tank is altered too rapidly, it could lead to the fish entering into pH shock. This condition is dangerous and can kill the fish.

5. What To Do When Your Fish Experiences pH Shock

Monitor the KH and pH levels with a reliable test kit as some kits give inaccurate readings, especially when measuring low kH levels. However, if you discover the KH is less than 4, add potassium bicarbonate or sodium bicarbonate hourly until the KH level rise.

Nonetheless, monitor that the pH level doesn’t increase to more than 0.3 during this time. Buffer the water, that’s how the pH remains stable at the level most convenient for the fish. A fish that experienced pH shock would take a while to recover fully and is susceptible to disease, so keep them comfortable during this recovery period.

However, if your KH is high, but pH keeps fluctuating rapidly, then chemicals may be seeping through decorations or the substrate. For long-distance fish transportation, add some water conditioners to reduce the effect. Additionally, do not open the bag until you are ready to put it in a tank.

6. How Can You Monitor the pH in the Aquarium?

A high-quality and reliable test kit is very important when monitoring your aquarium pH because it is very accurate. Testing is important because a low or high pH can affect water chemistry and quality, causing other parameters to become unstable.

Hence, get test kits as simple dip ones, and then you compare the coloration after the dip to the color chart that comes with the test kit. The color it shows indicates the pH level of the tank. Furthermore, you should follow instructions while using these test kits. If you do not, you could cause the test to give inaccurate readings.

Generally, to be sure of your readings, repeat the test a second time and compare both. If you are unsure about the result, get a reliable fish store to test a sample of your tank water.

7. What Is the Ideal pH for a Fish Tank?

There’s no “ideal” pH for a fish tank, as the pH depends on the fish species. Simply put, not one pH can suit all fish habitat needs. This is because they originate from different rivers, and oceans, these habitats have varying pH levels.

Nonetheless, species from similar habitats have the pH range they tolerate. Similarly, some different species from different habitats may tolerate the same pH range. For instance, freshwater fish enjoy the water with a pH range from 5.5 to 7.5, while saltwater species prefer alkaline water.

8. How Often Should I Test the pH Levels in My Fish Tank?

How to lower ph in aquariumYou should test the pH levels in your tank every two to four weeks. This would help you detect any changes. Additionally, you should check your pH if a fish dies in your tank and if you are administering medication to fish in your tank. It is important to check the pH levels to know the cause of death but remember that chemicals from medicines can alter pH.

Furthermore, check the pH when you change your tank filter. Nonetheless, you should keep a log of the different pH levels and times to help with referencing in the future. We also recommend you test in the afternoon to get the most accurate pH readings.


Note that fish species commonly thrive in the water close to their natural habitat. So, here are some tips to remember when you need to lower the pH in an aquarium:

  • Perform partial water changes frequently
  • Soak peat moss for some days to get rid of some of the colors it releases before adding it to your tank
  • Reverse osmosis lowers tank pH

Remember that fish species typically thrive in the water close to their natural habitat, the fish based on their habitat origin prefer particular pH levels. Nonetheless, frequently monitoring the levels and gradually lower pH to prevent shock and fish death.

5/5 - (17 votes)


Please enter your comment!
Please enter your name here