What Is The Best pH Level For Neon Tetras?

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Raising neon tetras is not a difficult task since these creatures are hardy and can thrive in various aquarium conditions.

However, adjusting the pH level can be a bit more challenging compared to other factors.

In this article, I will discuss the optimal pH range for neon tetras, factors that can cause pH fluctuations, and the steps you can take if the pH falls outside of the recommended range. 

Let’s dive right in.

The Best pH For Neon Tetras

This is what you should know when it comes to adjusting the optimal pH for neon tetras:

  • Ideal and Optimal pH: Neon tetras thrive best in a pH range of 5.0 to 7.5, with the optimal level being around 6.0 – 6.5. These acidic conditions reflect their natural soft-water habitats, bringing out vibrant colors and optimal health.
  • pH Stability and Extremes: The stability of pH is key for the well-being of neon tetras. Sudden pH fluctuations can cause stress and serious health issues. Extremes, either below 5.0 or above 7.5, may result in acidosis or alkalosis respectively.
  • Health Impact and Breeding Conditions: Long-term exposure to inappropriate pH levels can suppress neon tetras’ immune systems and make them more disease-prone. For breeding, slightly more acidic conditions (pH 5.0 – 6.0) are preferable to simulate their natural spawning grounds.

Also Read: Neon Tetra Tank Setup

Can Low pH Harm Neon Tetras?

Exposing neon tetras to low pH levels can lead to serious health issues:

  • Direct Health Impact: Extremely low pH, generally below 5.0, can harm neon tetras by causing a condition known as acidosis. This situation results in an excessive amount of acid building up in the fish’s bodily fluids.
  • Osmoregulation Difficulties: Neon tetras maintain a delicate internal balance of salts and other substances, known as osmoregulation. Highly acidic water conditions can disrupt this process, potentially leading to health issues.
  • Reduced Breeding Success: A very low pH environment may have a negative impact on the breeding success of neon tetras. It can interfere with egg fertilization and development, thus reducing the number of offspring.
  • Stress Induction: Neon tetras are sensitive to sudden changes in their environment. A rapid decrease in pH can induce substantial stress in these fish, subsequently compromising their immune systems and leaving them more prone to various diseases.

How To Measure The pH Level In Your Aquarium

  • Acquire a pH Testing Kit: Buy a pH testing kit from a pet shop or online. Make sure to buy a kit that is specifically designed for aquarium use. My recommendation: API FRESHWATER MASTER TEST (link to Amazon).
  • Prepare the Sample: Use a clean container to collect a small sample of the aquarium water. It’s essential not to contaminate the sample, so avoid touching the inside of the container or the water with your hands.
  • Conduct the Test: Adhere to the guidelines included with your testing kit. Usually, this will involve adding a few drops of a test solution or a test strip to the water sample.
  • Wait for the Reaction: Wait for the indicated amount of time in the instructions. This allows the test solution or strip to react with the water sample.
  • Read the Results: Compare the color of the water sample to the color chart that comes with the testing kit. This will give you the pH level of the water.

Now that you know how to test the aquarium water, let’s learn how to adjust the pH level.

How To Raise The pH Level In Your Aquarium?

Before attempting to raise the pH level, it’s best to temporarily remove your fish from the tank. Then, you can simply follow these steps:

  • Identify the Current pH Level: Start by testing the current pH level of your aquarium using a testing kit. You need to know your starting point before you can effectively raise the pH.
  • Get a pH Increaser: Purchase a pH increaser from a pet store or online. Ensure it’s suitable for aquarium use. Always follow the instructions on the packaging for proper dosages. My recommendation: API PROPER pH 7.0 (link to Amazon).
  • Apply a Small Amount: Add a small amount of the pH increaser to the aquarium. Start with less than the recommended amount to avoid a sudden, drastic change in pH.
  • Mix it Well: Stir the aquarium water gently to distribute the pH increaser evenly. This can help the solution work more effectively.
  • Wait and Test: After 24 hours, test the pH level of the aquarium again. This gives the pH increaser time to work.
  • Repeat if Necessary: If the pH is still too low, repeat the process. Remember, it’s better to raise the pH slowly over several days than to cause a sudden change.
  • Monitor Regularly: Once you’ve achieved the desired pH, continue to monitor the pH level regularly. This will help you maintain a stable, healthy environment for your neon tetras.

How To Lower The pH Level In Your Aquarium

If the pH in your neon tetras tank is too high, here’s how to lower it properly:

  • Determine the Current pH Level: Use your testing kit to ascertain the current pH level in your aquarium. This helps establish the amount of change needed.
  • Purchase a pH Reducer: Buy a pH reducer meant for aquarium use from a pet store or online. Follow the dosage instructions given on the package. My recommendation: API PROPER pH 6.5 (link to Amazon).
  • Add a Small Dose: Apply a small dose of the pH reducer to the aquarium. Always start with less than suggested to prevent a sudden pH drop which can stress the fish.
  • Disperse the Reducer: Gently mix the aquarium water to distribute the pH reducer throughout. This can aid the efficacy of the reducer.
  • Wait and Recheck: Allow 24 hours for the reducer to take effect before testing the pH level of the aquarium again.
  • Repeat as Needed: If the pH is still too high, repeat the process. It’s safer to decrease the pH gradually over several days rather than abruptly.
  • Keep Monitoring: After reaching the ideal pH, ensure to regularly monitor the pH levels to maintain a consistent and healthy environment for your neon tetras.

What Causes pH Levels To Drop?

If the pH level drops in your neon tetra tank, there are a few possible causes:

1. Biological Activities

  • The waste produced by your fish and any uneaten food can decay, leading to the production of acidic compounds that can lower the pH.
  • The nitrification process, a crucial part of the nitrogen cycle in the tank, produces nitric acid which can decrease the pH.
  • The overgrowth of certain bacteria and algae can also lead to acid production and a subsequent drop in pH.

2. Tank Substrate

  • Certain substrates, like peat or certain types of driftwood, can naturally acidify the water.
  • Some substrates may release minerals into the water that can affect pH levels.
  • Over time, decaying plant matter or detritus within the substrate can produce acidic compounds.

3. Tannins

  • Tannins released from driftwood, leaves, or peat can acidify the water, leading to a lower pH.
  • These natural compounds can also tint the water a yellowish-brown, which is sometimes desired for creating a “blackwater” environment.
  • Tannin-rich environments can be beneficial for some species but they should be managed correctly to avoid drastic pH drops.

4. Tap Water With Low pH

  • Some tap water naturally has a low pH, which will directly affect the pH level of your aquarium.
  • The pH can also be influenced if the water source has been treated with specific substances, such as chlorine or chloramines.
  • Regular water changes using this low-pH tap water can gradually decrease the pH of the aquarium over time.

What Causes pH Levels To Rise?

Several factors can cause a spike in water pH levels in your neon tetras tank:

1. High Carbonate Hardness (KH)

  • Water with high carbonate hardness acts as a buffer, resisting changes in pH and causing it to rise.
  • Tap water with a high KH level can lead to an increase in pH when added to the aquarium.
  • Certain substrates or decorations, such as crushed coral or limestone, can increase KH and subsequently raise the pH.

2. Lack of Carbon Dioxide (CO2)

  • A deficiency in carbon dioxide levels within the water can result in an elevation of pH.
  • In planted tanks, during the daytime, plants consume CO2 and release oxygen, leading to higher pH levels.
  • Inadequate aeration or limited plant growth can result in lower CO2 levels and a subsequent rise in pH.

3. Excessive Alkaline Substances

  • Some types of rocks, shells, or substrates can release alkaline compounds into the water, causing the pH to increase.
  • Overdosing alkaline additives or chemicals in an attempt to adjust pH can result in an unintended rise in pH.

4. Inadequate Filtration or Water Changes

  • Accumulation of organic waste and debris in the tank can contribute to rising pH levels.
  • Insufficient filtration or infrequent water changes can lead to the buildup of substances that raise pH over time.

Additional Water Requirements For Neon Tetras

The two other factors which are extremely important for neon tetras are the water temperature and hardness.

  • Water Hardness: Neon tetras thrive in soft water conditions. The optimal water hardness for these fish should be between 2 and 10 dGH and 1 to 2 dKH.
  • Temperature: Neon tetras favor temperatures that sit between 72°F and 78°F (or 22°C to 26°C). When you dip your hand into your aquarium, it should feel comfortably warm.

Also Read: Neon Tetra Temperature


Adjusting the pH for your neon tetras is a crucial step in maintaining optimal conditions for these fish, as they typically thrive in slightly acidic water with a pH range of 6.0-6.5.

If the pH falls outside this range, there’s no need to panic, as neon tetras are hardy creatures, and there are numerous ways to quickly adjust the pH to suitable levels.