Fishbowl Adviser

How to Safely Adjust pH in Your Aquarium

When it comes to adjusting the water quality parameters in your aquarium, adjusting the pH of the water is a significant factor that you must do properly. The pH value of your tap water might not be good for the type of fish you want to keep in your aquarium, so you’ll need to learn how to safely adjust the ph in your aquarium.

Stones and fish

What is pH and Why Is it Important for Aquariums?

In case you slept through the chemistry classes, pH is the measurement of how acidic or basic something is. In the case of aquariums, pH is the measurement of how basic or acidic the water solution you have in your tank is.

Alkalinity and acidity are measured on the pH scale to determine what type of water solution you have. The scale goes from 0 to 14, where 7 is neutral, anything below 7 is acidic, and anything above is basic.

Adjusting the pH Levels of the Water

When you set up your fish tank, you need to make sure the water parameters are suitable for your fish. The aquarium water’s pH levels need to be kept between 6.5 and 8.2, where the exact number of the level is based on the fish you have. You can ask your veterinarian to see what level you need and get any additional information about the water parameters you’ll need to set.

After you set the pH level of the water, you need to keep it consistent and stable. If there are any rapid changes in pH levels, your fish can experience harmful effects and even die. And make sure you do regular water testing as part of your aquarium maintenance to get ahead of any possible problems.

If you want to adjust the pH in your aquarium, you must do it before putting any fish in the aquarium. You’ll also need to test the water properly before you introduce your fish to the aquarium. If you already have fish in the aquarium, you shouldn’t make any sudden or drastic changes to the current pH or any of the other water parameters.

How to Increase the pH in the Aquarium

One of the most common methods of raising the aquarium’s pH levels is adding baking soda to the water. The safe amount is one teaspoon of baking soda for a 5-gallon tank to get a small incremental increase in pH. However, it’s best to remove your fish from the tank before you start raising the pH levels. Once you get the desired pH level, you can put your fish back and introduce them to the water carefully, just like it’s their first time. It’s important to remember that you must not make any sudden or large changes in pH if you want to avoid any severe effects.

You can also raise the pH levels with:

  • limestone or coral rock as decoration
  • crushed coral or dolomite gravel for the substrate that will slowly dissolve over time and slowly raise the pH levels
  • deionized (DI) or reverse osmosis (RO) water that will create the desired pH (but with proper testing, of course).

Black-yellow fish

How to Lower the pH in the Aquarium

The best and safest way to lower the pH levels in your aquarium is with peat moss. The tannins in the peat moss will lower the pH slowly and gradually. You just have to put the peat moss into a mesh bag and put it into the filter. However, the water may temporarily discolor with the addition of peat moss, but it will clear up over time. If you’re worried about your cloudy tank, you can use activated carbon to help it clear up faster.

You can also lower the pH levels with:

  • natural driftwood as decoration (but make sure you keep in mind that you will need a fair amount of driftwood, and not just one or two small pieces)
  • peat moss or peat pellets as an addition to the filter
  • decreasing aeration of the aquarium
  • deionized (DI) or reverse osmosis (RO) water that will create the desired pH (but with proper testing, of course).


  1. Water Chemistry – Aquarium Info
  2. pH and Ammonia Levels in Established Aquariums – PetMD


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