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How about a Blackwater Fish Tank?

Blackwater Fish Tank

Blackwater fish tank is a new trend. Not only do they look beautiful and unique, but they also have various beneficial features. For instance, they are antibacterial, soften the water, and reduce the pH and hardness of the water. It also plays a great role in breeding fish. You may have seen Betta fish owners keeping catappa leaves (almond leaves) for their development.

The black water tank is a term used for an aquarium with a dark atmosphere in the water. Even you will not be able to see the fish completely. In the wild like Eagle Creek in Wisconsin or Black Earth Creek, the fish grow in softer acidic waters. This is why these tanks are great for breeding some species of fish.

How to Set a Blackwater Fish Tank?

When you plan to set up your own blackwater tank, you need to consider certain factors, such as water chemistry, plants or decorations, and fish or inverts.

Water Chemistry

It is vital to manage certain chemistry of the water because a real blackwater has soft acidic liquid. The tannins can help you maintain the lower pH value, but if your tap water is very hard, you will also need to consider using reverse osmosis water.

Matching the original pH of blackwater streams and rivers may be considered unachievable because it can be 4.5 pH. However, if you manage to maintain a pH of 7 or lower than that, it will be enough to give comfortable surroundings to your plants and fish.

You can use leaves such as oaks or Indian almonds, alder cones, or driftwood for your aquarium’s look. You can easily soak, boil, and filter alder cones and leaves to get a blackwater extract. But you can also just put them on the bottom of the tank. They will slowly darken your water as they do in the natural habitat.

Fish and Invertebrates

You need to research properly before bringing any specie for the blackwater fish tank. It becomes more important if you are creating a certain pH. This way, only specific species of fish can live in your aquarium.

But if you are planning for a general dark water setup, any specie that prefers to live in dark water will work for you. Just don’t forget that all the fish should be compatible with each other. For instance, neon tetras and discus fish are best for blackwater aquarium, but that doesn’t mean you can keep them together. The tetras will become the dinner of discus fish without your knowledge.

Plants and Decorations

As you have learned that plants will help you create the blackwater biotope, it is important to bring the right plants. Like the fish, you also need to understand the natural distribution of plants.

If you don’t want to create the original blackwater, you can choose any plants that don’t need bright light. This doesn’t mean you only need plants that can live without light. You can choose plants that can live in dark and lower lights both. For instance, Anubias, Amazon sword, and Java fern are ideal for this type of tank. Moreover, floating plants such as Amazon frogbit can also help you create a realistic look with its long roots.

What Type of Fish Can You Use?

You will be surprised that most of the fish we keep in the traditional fish tank flourish more in the blackwater fish tank. Let’s take a look at some of the most known and popular species.

South America

  • Angelfish Discus fish
  • Corydoras catfish
  • German blue ram cichlid
  • Neon & cardinal tetras


  • Gourami
  • Dwarf pufferfish
  • Betta complex
  • Glass catfish
  • Kuhli loaches
  • Rasbora


  • Kribensis cichlid
  • Hemichromis cichlids
  • Congo tetra

What Other Things You Should Know about Blackwater Fish Tanks?

You need to understand that it may seem easy to turn the tank into blackwater, but you should not be too fast. Ensure not to affect any livestock. The humic acids and tannic acid emitted by the botanicals also help to lower the pH. If they are not releasing the acids rapidly, then it’s fine to keep them. You only need to check once in a while whether the pH value is the same as you desire.

Don’t forget to check the pH and kH at least twice a week. You can use liquid test to get the most accurate values. Moreover, checking the water condition is another factor you need to consider. Suppose you have removed 30% of the water. If you replace it with dechlorinated tap water, you may be diluting the tank. Not to mention, the water parameters will get changed. This means it can increase the pH value of water, depending on the tap water.

Compare different water conditions with your tap water. If they look very different, you need to rethink the idea. To solve this problem, you can prepare the water a few days before by using some botanicals. This way, you can create the exact or at least closer water parameters to avoid impacting livestock.

Bottom Line on blackwater fish tank

As you have learned the main aspects of the blackwater fish tank, you can easily make your own at home. You only need to find the right plant and species for your aquarium. Don’t forget to bring tools to check the pH and kH values of the water, which you will need to measure later in the process.


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