How To Add Bacteria To A Freshwater Fish Tank

by Aquarium Scoop | Last Updated: November 29, 2022

Want to learn how to add bacteria to your aquarium? Bacteria provide a healthy environment for your fish by reducing harmful toxins. Adding bacteria is easy!

In this guide you’ll learn:

  • What is bacteria?
  • How to add bacteria to a freshwater fish tank
  • Tips for maintaining bacteria levels

Did you know that adding bacteria to a freshwater fish tank can benefit your fish?

Bacteria can help keep your water clean and free of harmful toxins, providing a healthier environment for your fish. Plus, we’ll offer troubleshooting tips if you encounter any problems along the way.

What Is Bacteria and Why Do You Need It in Your Freshwater Fish Tank?

Bacteria are tiny, single-celled organisms that are found everywhere in nature. Although they are often associated with disease and illness, not all bacteria are harmful to you – in fact, many bacteria play an essential role in keeping your fish tank clean and healthy.

Without adequate levels of beneficial bacteria, your fish tank will quickly become overrun with harmful algae and toxins, which can lead to the death of your fish.

So, what are these beneficial bacteria, and how do they help clean your fish tank?

Beneficial bacteria are responsible for the process of nitrification, which is a critical element in the nitrogen cycle. Nitrification is the conversion of ammonia (produced by fish waste) into nitrites and nitrates. This process helps remove toxins from the water and makes it safe for your fish. Bacteria also play an important role in decomposition – they break down dead plants and animals, which would otherwise pollute the water.

Doing this helps keep oxygen levels high and maintain a healthy environment for your fish. Some types of bacteria even produce substances that can act as food or medicine for your fish!

As you can see, beneficial bacteria are essential for keeping your freshwater fish tank clean and healthy. If you’re setting up a new tank, you can introduce beneficial bacteria using gravel or other substrates from an established aquarium.

πŸ“šΒ Read More >> How Long To Wait Before Adding Bettas To A New Tank

Expert Tip 🧠

If you’re setting up a new tank, cut a piece of the filter from your old tank to put in your new filter. If your water parameters are the same, you already have a healthy colony of nitrifiers.

You can also purchase bacteria in a bottle from your local pet store. Once beneficial bacteria are in your fish tank, you must do everything possible to maintain their population. This means avoiding the use of chemicals and medications which can kill them off and performing regular water changes to keep the environment clean.

How to Add Bacteria to Your Freshwater Fish Tank – The Two Methods

Adding bacteria to your freshwater fish tank is an integral part of keeping your fish healthy and the water clean.

There are two main ways to add bacteria to your tank:

Add live plants

Adding a live plant is the more natural way to add bacteria, as it will introduce beneficial microorganisms into the water that will help to break down waste and keep the water clean.

To do this, choose a live plant suitable for your aquarium and place it in the tank. The plants will release beneficial microbes into the water over time, helping to keep things clean and tidy.

Bacteria supplements

Using a bacteria supplement is another option, which can be added directly to the water or food before feeding it to your fish. This method introduces large numbers of good-quality bacteria into the aquarium, which can quickly establish themselves in the system, breaking down waste products efficiently.

Bacteria supplements come in liquid and powder form – follow instructions on dosage depending on your chosen product. It’s okay to add more than the recommended amount, but don’t add more than double the recommended dose.

Expert Tip 🧠

Add bacteria directly to your canister filter while it’s on. For internal filters, apply bacteria near the filter for best results.

Maintaining the Correct Level of Bacteria in Your Freshwater Fish Tank Over Time

Tips for keeping bacterial levels where they should be:

5 Troubleshooting Tips for Adding Bacteria to a Freshwater Fish

If you’re having trouble adding bacteria to your freshwater fish tank, here are five troubleshooting tips that might help:

  1. Check the water temperature – bacteria thrive in warm water, so they won’t be as active if the water is too cold.
  2. Make sure there’s enough oxygen in the water – bacteria need oxygen to survive, so if the levels are low, they won’t be able to multiply.
  3. Add some organic matter – this can provide food for the bacteria and help them grow more quickly.
  4. Use a product specifically designed to add bacteria – these products usually contain live cultures that will immediately start growing in your tank once added.
  5. Try different types of bacteria if one strain isn’t taking hold in your system for whatever reason.


Can I add beneficial bacteria to my tank?

Yes, you can add beneficial bacteria to your fish tank. This will help keep your water clean and healthy for your fish.

You can purchase bacteria in a bottle at your local pet store or online. Be sure to follow the directions on the label when adding it to your tank.

How do you increase beneficial bacteria in an aquarium naturally?

There are a few ways to increase beneficial bacteria in aquariums naturally. One way is to add live plants to the tank. Plants help to aerate the water and provide a place for beneficial bacteria to grow. 

Another way is to add fish that eat algae, such as plecos or otocinclus catfish. These fish help keep the tank clean and also provide a source of food for beneficial bacteria. 

Finally, you can let your aquarium filter do its job; over time, it will become colonized with helpful bacteria.

What are good bacteria for a freshwater aquarium?

There are many different types of good bacteria for freshwater aquariums. Some common examples include Nitrosomonas, Nitrobacter, and Pseudomonas. These bacteria help to break down ammonia and nitrites, which can be harmful to fish if left unchecked. Good bacteria also consume organic matter and help to keep the tank clean.


It takes time for bacteria to colonize a new aquarium, so keep going if you don’t see results immediately. Aquarium Scoop offers various services to educate aquarium owners on taking care of their fish and other aquatic life. We provide educational seminars, one-on-one consultations, and group workshops. We also have an extensive online library of articles and resources.