The Fish Guru

Creating and Maintaining a Natural Blackwater Aquarium: Tips and Tricks

Aquariums are a great way to bring nature into your home and enhance your living space. However, one type of aquarium that many people overlook is the blackwater aquarium.

Blackwater environments are characterized by the presence of plant tannins and organic matter, which give the water a dark color and a pH level that is often more acidic than traditional aquariums. In this article, we will explore the different aspects of blackwater aquariums, starting with an overview of this type of environment and the fish species that thrive in it.

We will then look at the key steps in creating a blackwater aquarium, including tank size, substrate, water parameters, filtration, and lighting.

Definition and Characteristics of Blackwater Environments

Blackwater environments are typically found in rainforest regions, where decaying plant matter leads to the accumulation of tannins in the water. These tannins give the water a brownish color and a lower pH level than other types of water.

In a blackwater aquarium, the water is enriched with organic matter, which creates a more natural and authentic environment for fish. One of the key characteristics of blackwater environments is the presence of plant tannins.

These tannins come from decaying leaves, bark, and other organic matter, and can have a significant effect on the water’s pH level.

Tannins can also help to boost the immune system of fish, and can act as a natural antifungal and antibacterial agent.

Fish Species Suitable for Blackwater Aquariums

There are many different fish species that thrive in a blackwater environment. Some of the most popular fish to keep in a blackwater aquarium include neon tetras, corydoras catfish, angelfish, discus, kuhli loaches, cherry barbs, otocinclus, pacus, and silver dollars.

These fish are typically found in the wild in blackwater environments, and are well-suited to this type of environment in captivity. Neon tetras are some of the most popular fish to keep in a blackwater aquarium, due to their vibrant colors and peaceful nature.

Corydoras catfish are also a good choice, as they are bottom-dwellers that are well-suited to the dimly-lit environment of a blackwater aquarium. Angelfish and discus are larger fish that can add a stunning visual element to your aquarium.

Kuhli loaches are a great option for those who want to add some activity to their aquarium, as they are active fish that can swim freely in a blackwater environment.

Tank Size and Substrate

When it comes to creating a blackwater aquarium, the first step is to choose the right size tank. There are many different sizes to choose from, ranging from nano blackwater aquariums to larger tanks that hold hundreds of gallons of water.

The size of your tank will depend on the type of fish you want to keep, as well as the available space in your home. Once you have chosen the right size tank, the next step is to choose the substrate.

There are several options to choose from, including peat, freshwater sand, and marine gravel. It is important to choose a substrate that is pH-neutral and free of harmful chemicals that could harm your fish.

Water Parameters and Filtration

In a blackwater aquarium, it is important to maintain the right water parameters. This includes pH levels, which should be between 4.5 and 6.5, and temperature, which should be between 74F and 78F.

It is also important to maintain the right level of plant tannins in the water, and to use slow-release sources of tannins, such as driftwood or leaves. To keep the water clear and free of debris, it is important to use a good filtration system.

Canister filters are a great option for blackwater aquariums, as they can remove debris and impurities from the water while maintaining the right level of plant tannins. Activated carbon can also be used to help absorb impurities and keep the water clean.

Plants and Lighting

Finally, it is important to choose the right plants and lighting for your blackwater aquarium. Aquatic plants can add a beautiful visual element to your tank, and can help to maintain the right level of plant tannins in the water.

Some of the best plants for blackwater aquariums include Anubias, Java Fern, and Cryptocorynes. When it comes to lighting, it is important to choose a light intensity that is appropriate for your plants and fish.

Low to moderate light is typically best for blackwater aquariums, as it can help to maintain the natural environment of the tank. Walstad tanks, which use potting soil as a substrate, can be a great option for those who want to minimize the need for lighting and CO2 supplementation.


In conclusion, blackwater aquariums offer a unique and natural environment for fish, and can be a great way to enhance your living space. By following the steps outlined in this article, you can create a beautiful and healthy blackwater aquarium that provides a habitat for your fish to thrive.

Whether you are a novice or an experienced aquarium enthusiast, a blackwater tank is a beautiful and rewarding addition to any home.

Popular Fish Species in Blackwater Aquariums

There are plenty of fish species that thrive in blackwater aquariums. Some of the most popular include neon tetras, corydoras catfish, angelfish, discus, kuhli loaches, cherry barbs, otocinclus, apistogrammas, bee shrimp, and chocolate gouramis.

Neon tetras are a popular fish due to their bright, colorful appearance. They are also easy to care for and get along well with other fish, making them a great addition to any community aquarium.

Corydoras catfish are another popular choice, as they are bottom dwellers that help to keep the tank clean. Angelfish and discus are larger fish that are best suited for larger blackwater aquariums.

They are known for their stunning visual appeal and majestic swimming patterns, making them a popular choice for those who want a show stopping fish in their aquarium. For those looking for something a little different, kuhli loaches and cherry barbs are great options.

Kuhli loaches are very active and can add some movement to the aquarium, while cherry barbs are bright red in color and add a pop of color to the tank. Otocinclus are small, peaceful fish that are great for algae control.

They are known to clean the leaves of plants and surfaces in the aquarium. Apistogrammas are beautiful, colorful dwarf cichlids that thrive in blackwater environments.

They are known for their unique behaviors and will even change colors depending on their mood. Bee shrimp and chocolate gouramis are also popular choices for blackwater aquariums.

Bee shrimp are peaceful freshwater invertebrates that are available in a variety of colors and patterns. Chocolate gouramis are a unique fish with a distinctive chocolate brown color and iridescent scales.

They are more challenging to care for than other fish on this list, but can be very rewarding.

Large Blackwater Species

If youre looking for larger fish to keep in your blackwater aquarium, there are some great options available. Pacus and silver dollars thrive in blackwater environments, but have specific dietary requirements.

These fish are vegetarian and require a diet rich in plant matter. It’s recommended to supplement their food with vegetables, fruits, and aquatic plants.

Pacus and silver dollars can grow very large, so they require a large aquarium. Additionally, because they are herbivores, they may damage aquatic plants in the aquarium, which should be taken into consideration when choosing your species.


If youre interested in adding some invertebrates to your blackwater aquarium, there are several species to choose from. These include Bee shrimp, Bamboo shrimp, and Malaysian Trumpet snails.

Bee shrimp are a freshwater shrimp that are very peaceful and make great tank mates for other fish. They are typically small and delicate, so care must be taken when selecting other fish species to coexist in the aquarium.

Bamboo shrimp are filter feeders and are great for keeping the water clean in your blackwater aquarium. They are peaceful and do well in community tanks with other fish.

Malaysian Trumpet snails are hardy freshwater invertebrates that are ideal for blackwater aquariums. They have a hard shell made of calcium carbonate, which helps to buffer the water and maintain stable pH levels.


Plant tannins and humic substances are the most prominent factors in blackwater aquariums. These compounds create the signature look of the blackwater environment, producing dark, tea-colored water that is rich in beneficial organic compounds.

These compounds not only provide a more natural environment for fish but also act as natural antibacterial and antifungal agents. It is important to note that tannins will lower pH levels in the aquarium, which is characteristic of blackwater environments.

If the pH level drops too far, then the water will become too acidic for some fish to thrive.

Water Changes

Partial water changes are an essential part of maintaining a healthy blackwater aquarium. Regular water changes help to keep the general hardness (GH) and carbonate hardness (CH) of the water at appropriate levels.

It is recommended to use distilled water or reverse osmosis water for water changes and to add mineralization salts to help buffer the water. These salts help to stabilize the pH and maintain appropriate levels of calcium and magnesium.

Water Parameters and Filtration

Maintaining appropriate water parameters is key to the success of a blackwater aquarium. Water conditioners designed specifically for blackwater aquariums should be used to help maintain the correct pH level and tannin concentration.

In terms of filtration, canister filters are recommended as they provide high flow rates and are efficient at removing debris and impurities while maintaining the right level of plant tannins in the water. Activated carbon can also be used to help absorb impurities and keep the water clean.

It is important to place the carbon in a media compartment separate from the biological media to prevent bacteria from colonizing and rendering the carbon ineffective. The filter flow rate should also be kept low to prevent disrupting the peaceful environment of the blackwater aquarium and encourage the proliferation of beneficial bacteria in the aquarium.

It’s also important to use a test kit to test the water regularly, and to monitor aquarium parameters such as ammonia, nitrite, and nitrate levels. By adhering to these key steps and monitoring the health of your fish, you can create a beautiful and healthy blackwater aquarium that both you and your fish will enjoy.Blackwater aquariums offer a unique and compelling environment for fish, characterized by plants, organic matter, and a tea-colored hue.

While it can be challenging to maintain the ideal water conditions, it is well worth the effort for the stunning natural feel and direct experience of creating and observing the ecosystem. In this final section, we will look at both the advantages of blackwater aquariums and the challenges associated with this type of environment.

Advantages of Blackwater Aquariums

There are many advantages to keeping a blackwater aquarium. One of the most significant advantages is the unique look and feel of the aquarium.

The tea-colored water creates a natural and authentic environment that can provide an interesting change of pace from more traditional aquarium setups. Another advantage of blackwater aquariums is the ability to keep unusual species of fish.

Many types of fish, such as discus and apistogrammas, that originate in blackwater environments and require the specific conditions that blackwater aquariums provide. This natural environment can result in greater opportunities for natural breeding behaviors for fish.

Blackwater aquariums create an ideal environment for some aquatic plant species. The plant tannins that tint the water in blackwater aquariums create a natural environment that allows aquatic plants to thrive.

For the aquarist interested in creating a planted aquarium, a blackwater setup can be an excellent opportunity to experiment with different plant species.

Challenges of Maintaining Blackwater Aquariums

Maintaining a blackwater aquarium can be challenging. One of the major challenges associated with blackwater aquariums is the high level of dissolved organic material (DOM) that is present in the water.

Organics can accumulate over time, which can lead to a decrease in water quality and a potential increase in toxins. The solution to this challenge is to ensure proper cleaning routines that maintain water quality.

Removing organic debris especially old plant leaves can reduce the DOM level of the water and prevent the growth of harmful bacteria.

Invertebrates thrive in the organic-rich environment of blackwater aquariums, but they can also be challenging to care for in the long term. Texas tubes, as well as the internal crevices of rocks and driftwood, are potential sites for accumulation of minerals over time, which is a protective mechanism for snails’ shells.

However, it can cause the water in the aquarium to become too hard over time. Checking water parameters, such as water hardness and mineral content in addition to regular partial water changes are essential.

Soil and substrates play an important role in the health of the fish and plants. While soil is highly nutritious and boosts the growth of aquatic plants, it also can become a source of harmful pathogens as it can decompose over time.

It is recommended to replace the soil completely every four to five years or to add a thin layer of new soil over the old one. Concerns may occur on soil types in which they can release high levels of nitrogen into the water which could lead to the growth of algae.

Long term soil and substrate maintenance must be included in aquarium husbandry.


Blackwater aquariums offer a unique and natural environment for fish and can be a stunning addition to any home. Though maintaining a blackwater aquarium can be challenging, adhering to the proper maintenance procedures and monitoring water parameters can make it manageable.

The rewards of blackwater aquariums include unique and unusual fish species, aquatic plant systems, and a natural feel, which provides both a visual and an ecological experience for the aquarist. In this article, we have explored the various aspects of blackwater aquariums.

We’ve looked at the definition and characteristics of blackwater environments, the different fish species suitable for these aquariums, and the crucial steps involved in creating and maintaining them. We’ve also discussed the advantages of blackwater aquariums including a natural feel, unique fish species, and ample opportunity for aquatic plant growth, as well as the challenges of maintaining this specific environment.

It is essential to maintain water quality, soil and substrate quality, and monitor water parameters to ensure the success of a blackwater aquarium. By adhering to these essential steps, anyone can create a healthy and beautiful blackwater aquarium that brings the wonders of nature right into their homes.

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