How to Raise pH in Aquarium: A Guide for Beginners

If you are new to fishkeeping, you might have heard about the importance of maintaining the pH level of your aquarium water. pH is a measure of how acidic or alkaline the water is, and it can affect the health and well-being of your fish. Different fish species have different pH preferences, depending on their natural habitats. For example, most tropical fish prefer a pH range of 6.5 to 7.5, while some cichlids and goldfish thrive in alkaline water with a pH above 7.5.

But what if the pH in your tank is too low? How can you raise it safely and effectively? In this article, we will explain the causes of low pH in aquariums, the methods to raise it, and the precautions to take when doing so. By following these tips, you can ensure that your fish enjoy a comfortable and stable environment in your aquarium.

how to raise ph in aquarium

How to Raise pH in Aquariums?

If you have tested your water and found that the pH is too low for your fish, you need to act quickly but carefully to raise it. A sudden change in pH can shock or even kill your fish, so you need to make sure that you raise it gradually and monitor it closely. Here are some methods that you can use to increase the pH of your aquarium water:

  • Change the water: One of the simplest and most effective ways to raise the pH of your tank is to perform regular water changes with dechlorinated tap water that has a higher pH than your tank water. You can use a gravel vacuum to siphon out about 10% to 20% of the water every week or two, depending on the size and bioload of your tank. Then replace it with fresh water that has been tested and adjusted to match the temperature and hardness of your tank water. This will help dilute the acidic substances in your tank and stabilize the pH.
  • Add bicarbonates: Another way to raise the pH of your tank is to add bicarbonates, which are alkaline substances that buffer the water and prevent pH swings. You can use baking soda (sodium bicarbonate) or crushed coral (calcium carbonate) for this purpose. Baking soda is cheap and readily available, but it can also raise the hardness of your water and affect some fish species. Crushed coral is more natural and long-lasting, but it can also increase the calcium levels in your water and cause algae growth. To use either of these methods, dissolve a small amount (about 1 teaspoon per 10 gallons) of baking soda or crushed coral in some tank water and add it slowly to your tank over several days until you reach the desired pH level.
  • Use commercial products: If you prefer a more convenient option, you can also use commercial products that are designed to raise the pH of aquarium water. These products usually contain buffers and minerals that balance the water chemistry and increase the alkalinity. You can find them in liquid or powder form at most pet stores or online. However, be careful not to overuse them as they can also alter other parameters of your water, such as hardness and salinity. Always follow the instructions on the label and test your water before and after using them.
  • Add alkaline materials: Another method to raise the pH of your tank is to add some materials that naturally release alkaline substances into the water. These include limestone, marble, shells, coral, or aragonite sand. You can use these materials as decorations or substrates in your tank, but make sure that they are clean and free of any contaminants. Also, keep in mind that these materials can take a long time to affect the pH and may also increase the hardness and calcium levels in your water.
  • Improve aeration and circulation: As mentioned earlier, poor aeration and circulation can lower the pH of your water by increasing the carbon dioxide levels. To prevent this, you need to ensure that your tank has adequate equipment that provides oxygen and movement to the water. You can use filters, pumps, powerheads, or airstones for this purpose. You can also add some live plants to your tank, as they can absorb carbon dioxide and produce oxygen during photosynthesis.

Precautions to Take When Raising pH in Aquariums

While raising the pH of your tank is necessary for the health of your fish, you need to be careful not to cause more harm than good. Here are some precautions that you should take when adjusting the pH of your aquarium water:

  • Test your water regularly: Before you attempt to raise the pH of your tank, you need to test your water to determine the current pH level and the optimal pH range for your fish. You can use a liquid test kit or a digital meter for this purpose. You should also test your tap water and any other water source that you use for your tank. You should test your water at least once a week or whenever you notice any signs of stress or illness in your fish.
  • Raise the pH gradually: One of the most important rules of fishkeeping is to avoid sudden changes in water parameters, as they can shock or even kill your fish. This applies to pH as well. You should never raise the pH of your tank by more than 0.2 units per day or 0.5 units per week. If you need to raise it by more than that, you should do it over several days or weeks, depending on how much you need to increase it.
  • Acclimate your fish: If you have new fish that require a different pH than your existing tank, you need to acclimate them properly before adding them to your tank. You can use a drip acclimation method, which involves slowly adding small amounts of tank water to a container with the new fish until they are used to the new water conditions. This can take anywhere from 15 minutes to several hours, depending on how different the pH levels are.
  • Monitor your fish: Even if you follow all the steps and precautions mentioned above, raising the pH of your tank can still cause some stress or discomfort to your fish. Therefore, you need to monitor them closely for any signs of distress, such as gasping, darting, hiding, or losing color or appetite. If you notice any of these symptoms, you should check your water parameters again and make any necessary adjustments.

What Causes Low pH in Aquariums?

There are several factors that can lower the pH of your aquarium water over time. Some of these are:

  • Lack of maintenance and cleaning: If you neglect to change the water regularly, remove fish waste, leftover food, and other debris, or clean the filter media, you are creating a breeding ground for bacteria and fungi that produce acidic substances. These substances can lower the pH of your water and also cause ammonia and nitrite spikes, which are harmful to your fish.
  • Acidic tap water: Depending on where you live, your tap water may have a low pH due to various reasons, such as soil composition, industrial pollution, or water treatment processes. If you use this water to fill or top up your tank without testing or adjusting its pH, you may end up with acidic aquarium water.
  • Poor aeration and circulation: Oxygen is essential for the health of your fish and the biological filtration of your tank. If the water is not well-aerated and circulated, carbon dioxide can build up in the water and lower its pH. This can happen if you have inadequate or faulty equipment, such as filters, pumps, or air stones, or if you overcrowd your tank with too many fish or plants.
  • Excess tannins: Tannins are natural compounds that leach from some organic materials, such as driftwood, peat moss, almond leaves, or pine cones. They can give your water a brownish tint and lower its pH. Some fish, such as bettas and tetras, actually benefit from tannins as they mimic their natural habitats. However, if you have fish that prefer alkaline water, you may want to avoid or limit these materials in your tank.


Raising the pH of your aquarium is not a difficult task if you know what causes it to drop and how to fix it. By using one or more of the methods described in this article, you can increase the pH of your tank safely and effectively. However, you should always remember that stability is more important than accuracy when it comes to pH. As long as you keep the pH within a suitable range for your fish and avoid drastic fluctuations, you can ensure that your fish are happy and healthy in your aquarium.