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Blackwater Aquariums are also known as Blackwater Aquarium biotopes. These are a beautiful choice for those who are looking for a unique looking aquarium. It is a type of aquarium where the water inside the tank is not completely clean or the tank is covered with lights. These are a true depiction of the natural habitat of most fish species. A lot of aquarium fish species come from these blackwater natural habitats. These are the places where there is low availability of light that reaches the bottom of the habitat. It happens because of water pollution, or sometimes because there are some elements present in the water that change the color of water in these natural habitats.

Ewkaa, CC BY-SA 4.0, via Wikimedia Commons

To better understand this, let’s take the example of maple leaves that fall from trees and reach the water bodies nearby. These leaves decompose in that water and change the color of the water from transparent to partially black. These leaves cause small changes in the chemistry of water and this allows the species of fish that live in these water bodies to adjust to this type of habitat. The Blackwater Aquariums are created by replicating these same conditions inside the tank. Read the article below to know more about these aquariums, and how to create and maintain them.

What Is A Blackwater Aquarium?

Blackwater ponds and streams are a habitat of many fish species in Asia and South America. All of these fish species live in a specific type of environment that has unclear or non-transparent water. Because this water is non-transparent, it does not allow the light to travel through, making the water appear almost black. Fish species that live in these conditions can also live in aquariums, but to keep them in your aquarium, you will have to provide them with a Blackwater Aquarium.

A Blackwater Aquarium is a tank full of decomposing leaves that change the color of water in your aquarium, making it look blackish. It helps you replicate the living conditions of some fish species that are only found in the blackwater habitats in Asia and South America. Decomposing leaves not only changes the color of the water, but also the pH, and chemistry of the water. So, they create a specific type of habitat where only a handful of fish species can live. If you are creating such an aquarium, you should get those specific fish species.

Blackwater Aquarium Biotope

Biotope Aquariums are the ones that are created according to the exact details of the natural habitat of a fish species. A Blackwater Aquarium biotope is created according to the details or specifics of the blackwater habitats of fish species. These not only look unique and beautiful but also work excellently in providing the fish a close to natural habitat condition. You have to use a specific set of things to create and maintain a Blackwater Aquarium biotope. These specific things are related to the natural habitat of the fish. For example, some fish respond well to almond leaves, while some prefer living in a blackwater biotope that contains maple leaves.

Blackwater habitats in nature have very little motion in the water. It prevents the water from moving out and also prevents the clean water from moving in. It usually happens in specific ponds near the river or places where there is an unconnected water body. This type of habitat not only causes the leaves to quickly decompose but also retains the chemicals that are involved in the process of decomposition. Hence, it changes the chemistry of the water. This change is very important for these fish species as they have adapted to it.

So, if you are making a Blackwater Aquarium biotope, you will have to make sure to use a slow filtration system. A slow filtration system would keep the movement in your tank low, and it would also filterless water. This would allow more decomposition in your tank, and it will make your tank look more real. Also, the fish would respond well to a slow-moving Blackwater Aquarium biotope as compared to rapid or fast-moving tank water.

Creating A Blackwater Aquarium

If you are looking forward to creating a Blackwater Aquarium biotope, you can do it with the following instructions. It is a fairly complex procedure that requires using a specific set of things, such as a tank, decorations, plants, and a filtration system. Below are complete details about creating a perfect Blackwater Aquarium habitat for your fish species.

●     Tank Size

The first step here is to select an appropriately sized tank. If you want to create a Blackwater Aquarium, you need to select a tank that is large enough to contain all plants, decorations and still provides enough space for your fish to swim and explore. You need to consider multiple factors such as the total number of fish, and the fish per gallon ratio of the tank members. If you want to keep more than one type of fish in your aquarium, you will have to calculate the average of fish per gallon among these fish species.

After you have known the number of fish, and fish per gallon ratio, you can multiply them to get the appropriate size for your tank. For example, if the fish per gallon ratio of your fish is 1 fish for 5 gallons, and you have 10 fish, you will need a 50-gallon tank. If you have multiple fish from different species, you will have to calculate their average fish per gallon ratio. To do that, you will need to add the fish per gallon ratios, and then divide them by the total number of fish.

For example, if one fish species needs 5 gallons per fish, and the second one needs 7 gallons per fish, you will need to calculate the sum of these numbers which is 12, and then divide it by 2. The answer will be 6 gallons, and if you have a total of 8 fish in your tank, you will need 48 gallons. It is not very complex math, you can easily do it according to your specific requirements. After you have selected a tank, it will be time for you to start creating a tank set up inside the tank.

●     Decorations

There are a lot of decorations that you can use for the Blackwater Aquarium biotope, for example, you can use botanicals, driftwood, plant leaves, caves, and hiding spots. Some people also use artificial grass to create a soft bottom. But you can choose to plant the real grass or plants in your Blackwater Aquariums. Apart from leaves, there are also elder cones that can help you create a blackish look inside your tank. These cones contain certain pigment chemicals, and when you put them in the water, these chemicals decompose and dissolve. It creates a dark black-looking aquarium.

You can decoratively use these decorations as well, for example, you can create caves and mountains inside the tank using stones, and cement. You can create fake-looking trees with the help of driftwood inside the tank. All of these decorations will make your look and feel more interesting. Also, they would help your fish when they need a safe hiding place. Your fish can hide in caves, along with driftwood, and decorations that you put in the tank. These are the reasons you need to carefully select the decorations for the Blackwater Aquariums. Also, you may have to select specific decorations or products that are only suitable for one fish species.

You should know that all of the fish species that live in Blackwater Aquariums have different living conditions and parameters. For that reason, you need to select appropriate items that are specific to that species. For example, plants, leaves, cones, or anything else. Fish that live in those areas where cone pines are common, would need a cone pine Blackwater Aquarium, meanwhile, fish that live in the areas where there are a lot of almond leaves, would need those specific almonds leaves. If you ignore this, it can negatively impact the health and lifespan of your fish.

●     Filtration System

The filtration system is one of the main components of any aquarium. It helps you cycle the water and clean your tank. It also helps you provide more oxygen and flow inside the tank. But in the case of a Blackwater Aquarium, you do not need to provide flow. So, you will have to use a slow filtration system that cleans your water without vibrating or with less vibration. Put the filtration system inside the tank and use it in the slowest settings. To provide more oxygen in the tank, you may have to use an oxygen pump. More oxygen supply would simply increase the rate of decomposition in your aquarium, making it more black and changing the chemistry of the entire tank.

In a normal tank, setting up a filtration system is fairly easy. You just need to put the filter inside the tank, enter the settings, and activate it. But in the case of the Blackwater Aquarium, it is difficult. You need to keep the water in a Blackwater Aquarium dense, and you can only do that if there is dissolved matter in your tank. For that reason, you need to set up your filtration system in a way that retains most of the aquarium water inside the tank. If you are using a canister filter, you should remove the activated carbon absorber. It would help you retain most of the material inside the tank while filtering.

It would cause multiple issues such as a higher concentration of ammonia and other harmful chemicals that can kill your fish, but there is also a solution for this problem. To keep the blackness of your aquarium, and keep the water clean, you will have to cycle or change the water more often in a Blackwater Aquarium tank. This would help you maintain proper chemistry inside your tank.

●     Temperature Control

Apart from the filtration system, you also need to put something in your tank to monitor and control the temperature. For this purpose, a lot of people use digital thermometers built for aquariums. These devices allow you to monitor the temperature. Some of these devices also act as heaters inside your tank to warm it up when you need a higher temperature. For example, if you are living in a cold area, where the temperature can go below a certain range that is not suitable for your fish. You will have to use a heater to keep the temperature within a certain range in those areas.

But if you live in a warm region, where the water temperature can be higher than the given limits. You will have to deploy some measures to keep your tank temperature cool or within a given limit. Many expert fish keepers put ice cubes to lower the temperature of their tanks. It works perfectly fine. You just need to make sure that you only put a small number of ice cubes that can lower the temperature to a certain degree. It might feel like an unconventional method for keeping your tank cool, but it is one of the most effective cooling methods.

●     Plants For Blackwater Aquarium

There are a lot of plants that can grow in the low light conditions of Blackwater Aquariums. You just need to make sure that you select a plant that is compatible with your fish species. These plants will produce more oxygen that will dissolve in the water and would increase the rate of decomposition in your tank. It would help you make your tank look more black. A lot of fish keepers intentionally put some dead plants in the aquariums. Also, if any plant in your Blackwater Aquarium is dying, you should not remove it and allow it to die and rot in the water. This is a way of making your tank black through natural means. Here is a list of the plants that you can put in your Blackwater Aquarium biotope.

  1. Hydrophilia
  2. Amazon sword
  3. Pygmy chain sword
  4. Anubias nana
  5. Cryptocoryne
  6. Java Fern

Apart from these, you can use other suitable plants of your choice. But make sure that these plants are capable of living in dark conditions. You only need a few plants that would die and decompose. So, selecting all plants that can decompose in blackwater conditions would be a bad choice. 

●     Water Chemistry – Parameters

The water chemistry of Blackwater Aquariums is one of the most important factors that you need to look after. There are certain chemical levels that you need to maintain inside your tank. For example, a specific pH level is very important for keeping your fish alive in the tank. Any changes in the pH would change the chemistry of water and that would kill your fish. A lot of Blackwater Aquariums are acidic, but some are also basic. So, you need to make sure that your fish can live at a specific pH and then try to maintain that pH level in your tank.

Several techniques can help you maintain the pH in your tank. For example, if your tank becomes highly acidic, you can use calcium-based alkaline materials to lower the pH levels of that tank. Similarly, if a tank becomes too alkaline, you will have to use acidic materials to neutralize the alkaline effect. pH is not the only important factor in water chemistry that you need to maintain. Other important factors include the water hardness, which can be controlled with the help of proper filtration and change of water after a specific interval.

Fish For Blackwater Aquarium

There are a lot of fish species that live in the Blackwater Aquariums. These fish species originate from different parts of South Asia and South America. Most of them live near mountainous regions. They live in those places where water can form small disconnected ponds and aquifers of slow-moving water. It allows the creation of perfect habitat for these fish. When leaves from nearby trees fall in the water, and matter inside the water starts to decay, it creates a perfect habitat and living conditions for these fish. Here is a list of these species.

  • Neon Tetra Fish: A small and beautiful fish species that live in freshwater habitats. It can live in the Blackwater Aquariums. This type of habitat has perfect pH and hardness that is suitable for this species. That is why a lot of fish keepers select them as their first choice for a Blackwater Aquarium. But, you won’t be able to enjoy their beauty if the water inside your tank is not clear.
  • Cardinal Tetra Fish: It is another tetra fish species that can live in freshwater aquariums including Blackwater Aquarium biotopes. This is a small species of fish with beautiful features. It can be kept in small tanks and it has easy care guidelines.
  • Silver Dollar Fish: Silver Dollar fish is also a beautiful fish species that you can keep in a Blackwater Aquarium biotope. It is a fish species from South America, where there is an abundance of blackwater natural habitats where this fish thrives. So, keeping it in a Blackwater Aquarium biotope will help you replicate the natural habitat of this fish and would allow you to extend its lifespan and keep it healthy.
  • Angelfish: Angelfish is loved by everyone and is one of the most common fish species that you can find in aquariums. It is native to tropical regions of South America. Its natural habitat consists of slow-moving water that is deep and dark for the most part. That is why you can keep it in the Blackwater Aquarium biotopes as it has adaptations that allow this fish to live in such conditions.
  • Guppy Fish: Guppies are also some of the most beautiful, and most common fish species. It is loved by aquarium keepers as it is a small and peaceful fish species that can live in both normal aquariums and Blackwater Aquariums.
  • Betta Fish: Betta Fish is also one of the most popular aquarium fish that you can keep in your aquarium. It is a fish species that require dark conditions because its natural habitat is dark. So, keeping it in a Blackwater Aquarium is a perfect choice. It would look beautiful in a blackish background and dark aquarium light conditions.

Apart from these few species, there is a huge list of species that you can use for the Blackwater Aquariums. Most of the fish species that are found in normal aquariums, can be kept in Blackwater Aquariums. So, if you want you can test your fish in the Blackwater Aquarium. If it remains healthy, active, and can survive the conditions in the Blackwater Aquarium, you can keep it in the Blackwater Aquarium. This small test can help you find out which one of your aquarium species can be kept in the Blackwater Aquariums.

Invertebrates For Blackwater Aquarium

Apart from fish species, there are a lot of invertebrate species that you can keep in the Blackwater Aquariums. Blackwater Aquariums help extends the lifespan of these creatures as they can hide in the darkness. Here is a list of the most popular invertebrate choices for Blackwater Aquariums.

  • Bamboo Shrimp
  • Malaysian Trumpet Snails
  • Bee Shrimps
  • Assassin’s Snail
  • Rabbit Snail

There are many other options as well, but most of the invertebrates do not do very well with the fish species. They are too small and are often eaten by the fish in their tanks. So, it is up to you if you want to put snails or shrimps in your Blackwater Aquarium or not. You should also be aware that the population of snails will grow exponentially in your tank, and they can soon overtake the whole Blackwater Aquarium if you do not control their population spread.

How To Control Changes In Blackwater Aquariums?

As you know, Blackwater Aquariums contain decaying leaves and plant matter. Decomposition is a process that can alter the whole ecosystem inside your aquarium. For example, it can change the pH levels, amount of ammonia, and other harmful chemicals in your tank. Also, it would cause the carbon dioxide level in your tank to rise. All of these changes can kill or harm your fish in the tank. For example, any change in the pH levels that is not suitable for your fish would cause stress, diseases, and death.

Similarly, a higher concentration of harmful chemicals or carbon dioxide in your Blackwater Aquarium can also cause stress and death. Such an environment is also very suitable for the growth of bacteria and pathogens that can kill your fish. That is why you need to control these changes in your Blackwater Aquarium. Some strategies can help you control these changes. For example, cycling the water, and using a filter can help you maintain the parameters such as pH levels, hardness, and water chemistry. You can use oxygen pumps and a large surface area to make sure that your fish gets enough oxygen.


Blackwater Aquariums should be the first choice if you want to provide your fish a completely natural-looking habitat because many fish species live in blackwater habitats. So, a Blackwater Aquarium biotope will be similar to their natural habitat and they would benefit from it. Also, the Blackwater Aquarium habitat looks very beautiful. Some people add a colored substrate and yellow or dark brown lights to make the tank look dark and amazing. If you are a new fish keeper, you should know that it is very difficult to create a Blackwater Aquarium and it is even more difficult to properly maintain it. For that reason, you should do complete research about building it and keeping the fish in it.


Question: What are the benefits of a Blackwater Aquarium?

Answer: Blackwater aquariums are not just used for beauty, they also have other benefits. For example, a lot of fish species live in blackwater habitats, these aquariums can provide them similar conditions. Apart from that, these tanks have antibacterial properties that help you keep your fish healthy. Some of these are also used for breeding fish species.

Question: How to create a Blackwater Aquarium?

Answer: You need to start with filling your tank with appropriate amounts of water and decorations and everything else that you want to put in the tank. After that, you should add dead leaves or cone pines in your tank to make it look black.

Question: What plants to use for a Blackwater Aquarium?

Answer: There are a lot of aquatic plants that you can use for blackwater aquariums. For example, you can use java ferns, amazon sword, Anubis nana, and many others.

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