Blackwater Aquarium: The Complete Guide

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Are you an aquarium enthusiast looking for a new challenge?

If so, creating and maintaining a blackwater aquarium is something you may be interested in. 

Unlike typical, brightly-lit whitewater tanks, blackwater aquariums are dark and resemble natural-looking habitats that you may find in the Amazon Rivers. 

In this in-depth blackwater aquarium guide, we will discuss:

  • What a blackwater aquarium is
  • How to set one up with the necessary supplies
  • Best plants and fish for a blackwater aquarium
  • And blackwater aquarium benefits

Let’s dive in! 

Blackwater Characteristics 

There are many different blackwater biotopes that can be created in an aquarium. However, all blackwater aquariums have a few characteristics in common. 

For instance, all of them have dark water that closely resembles a dark tea-colored tint. 

The darkness in the water comes from tannins, which occur naturally in plants from their branches, leaves, and other waste. 

When plants, logs, branches, and leaves sit in water for long periods of time, they start to decay. After this happens, a mix of organic compounds is released into the water to create the dark appearance of blackwater.

Blackwater is also soft and acidic with a lower pH than whitewater. 

Blackwater aquarium fish
Source: Reddit u/KyleC66

What is a Blackwater Aquarium? 

A blackwater aquarium is a dark water aquarium that closely resembles blackwater rivers, streams, and ponds that are most commonly found in the Amazon. 

Unlike a typical whitewater aquarium where the water is clear, blackwater aquarium water is dark and murky like a dark tinted tea. 

This is due to the release of natural acids and dissolved humic substances. These substances come from the large amounts of leaf debris, decomposing wood, and other organic matter in the water.

Many species of fish will benefit from these conditions as well. 

A blackwater aquarium closely resembles their native environment, which can help reduce their stress and encourage breeding. 

Overall, creating and maintaining a blackwater biotope is a great challenge for hobbyists who are looking to expand their skills. 

Blackwater Aquarium Supplies

Before setting up a blackwater aquarium, there are some materials you will need.

Here is a list of supplies you will need to get started: 

  • Tank 
  • Substrate 
  • Lighting equipment 
  • Heater 
  • Filter
  • Powerhead or canister filter 
  • Water test kits 
  • Tannin & humic acid sources (peat, driftwood, Indian Almond Leaves, bottled tannins, leaf litter, decaying plant matter) 
  • Distilled or reverse osmosis (RO) water
  • General hardness (GH) reducing resins
blackwater aquarium with fish
Source: Reddit u/KyleC66

How to Set Up a Blackwater Aquarium 

Setting up a blackwater aquarium may seem intimidating. Here are the basic steps and supplies you will need to set up your own blackwater biotope. 

Tank Size

Blackwater aquarium tank size does not matter. 

You could choose to create a nano blackwater tank or a tank that holds a few hundred gallons! 

The choice is yours based on how much room you have and what you are comfortable with. 

Substrate 

It’s best to use a fine gravel to help anchor your plants and provide a root zone for your blackwater tank. 

You can choose a light, natural gravel, or dark gravel that is specifically for planted aquariums. 

Try to avoid using sand, as it will be more difficult to anchor your plants in. 

Many Amazonian fish tend to search through fine gravel in the wild to find live foods. So this type of substrate is the most realistic to their native environment. 

Lighting

In the wild, blackwater environments are typically found under lush forest trees that provide a canopy over the water. 

This means that a blackwater biotope should be shaded and dimly lit to recreate the effect of natural blackwater environments. 

Colored or day-light LED lights with settings that can create light ripples throughout the aquarium provide the best light for these types of aquariums. This will mimic the natural environment where sunlight shines down through the Amazon jungle trees. 

Dimly lit or medium bright LED lights will also help your aquatic plants thrive as well. 

Try out a few different light settings to determine which ones work best with your tank to bring out the color of your fish. 

Heater

The tropical fish in your blackwater aquarium need warmer water temperatures to thrive. 

It’s best to use a simple submersible heater for your tank that will keep the water temperature between 75-80℉. 

Filtration

A mechanical filtration system is necessary for your blackwater aquarium to help capture and remove excess debris and other waste. 

You may also consider using activated carbon filtration for one week out of each month to remove humic substances and other organic buildup. 

If your tank becomes too dark, simply increase the use of the activated carbon and change it weekly to avoid water staining. 

Make sure to keep an eye on your mechanical filter as well and change out the sponges, pads, or foam pieces once per month or less if needed. 

Water Conditions

Blackwater aquariums require soft, acidic water with low general hardness (GH). Realistically, matching the same conditions as blackwater rivers is not an easy task. 

You will want to make sure the pH levels stay at 7 or lower. 

Tannins in the water can slightly lower the pH, but if you have hard tap water at home, you may consider using reverse osmosis water to help provide the right water parameters.  

Using slow-releasing humic substances when setting up the tank for the first time can help you reach these water conditions over time. These substances include driftwood, peat, Indian Almond leaves, and alder cones. 

It’s important to test the water regularly with low-range pH test kits and water hardness test kits. 

Water Movement

Water movement is very important in a blackwater tank.

Smaller tanks will only require a small hang on the back power filter to create the perfect water movement. Larger tanks will need a canister filter or a powerhead to ensure the entire tank has an even flow of water. 

If you choose to have live plants in the tank, make sure your filter or powerhead does not disturb the water surface too much. 

This will drive off the carbon dioxide that live plants need.  

If you don’t choose to keep live plants, the water can be aerated as much as you prefer. 

Driftwood

In whitewater tanks, it’s required to clean, treat, and sterilize the wood before you put it into the tank. 

One benefit of a blackwater tank is that you don’t have to treat the wood first, as long as it is driftwood that is aquarium safe. 

You shouldn’t even boil the aquarium-safe wood, as you want the tannins to naturally release into the water. 

Manzanita wood is a great option because it is pH-neutral and looks beautiful in blackwater tanks. 

Rocks

Rocks can also be used in your blackwater tank, as long as they are treated. This will prevent the release of calcium, alkalinity, and microbes being released into the water. 

Avoid placing sharp or jagged-edged rocks in your tank as well, as this can harm your fish. 

Any smooth, treated rock will be fine. 

Leaf Litter

Leaf litter is one of the best ways to create blackwater in your aquarium. 

But it’s important to choose the right leaves to add.

Here are some of the best options to add to your tank: 

  • Alder Cones
  • Indian Almond leaves
  • Hawthorn
  • Japanese maple
  • Red oak
  • Turkey oak
  • Sessile oak
  • European beech
  • Pedunculate

You don’t need many leaves to reach the desired effect in your blackwater aquarium.

Start with about two leaves for every 10-15 gallons and add a few more if necessary. This organic matter is non-toxic, so you don’t have to worry about harming the tank.

Replace the leaves every few months. 

Source: Reddit u/KyleC66

Best Blackwater Aquarium Plants

An important part of setting up a blackwater aquarium is considering which plants, if any, you want to include in the tank. 

Blackwater biomes closely mimic fast-flowing streams where there aren’t a ton of plants or vegetation growing in the water. 

Therefore plants in a blackwater aquarium are typically not necessary and can cause issues that can easily be avoided.

However, if you love live plants and still want to add them to your tank, it’s best to choose low-light aquarium plants such as:

  • Anubias
  • Amazon frogbit
  • Bucephalandra
  • Cryptocoryne
  • Hygrophila 
  • Java fern
  • Java Moss
  • Pygmy Chain Swords
  • Water sprite
  • Taxiphyllum

Best Fish for a Blackwater Aquarium

The last part of setting up one of these tanks is finding the best fish for a blackwater aquarium.

Many different species thrive in a blackwater environment. This means there are many to choose from for your at-home blackwater aquarium. 

Here are some common fish that do well in blackwater aquariums: 

  • Betta fish
  • Tetras (Ember, Neon, Cardinals, Congo, etc.)
  • Dwarf Cichlids
  • Firemouth Cichlids
  • Kribensis Cichlid
  • Hemichromis Cichlids
  • Corydoras
  • Discus
  • Angelfish
  • Hatchetfish
  • Geophagus
  • Brycon species
  • Pimelodus catfish
  • Loricariid catfish
  • Uaru
  • Barbs
  • Danios
  • Apistogramma
  • Knife fish
  • Gouramis
  • Glass catfish
  • Dwarf loach
  • Kuhli Loach
  • Rasboras
  • Dwarf Puffer Fish

It’s important to research individual species to make sure they are fish that can thrive in a blackwater environment before adding them to your blackwater biome. 

Blackwater Aquarium Benefits 

Not only are blackwater aquariums a fun and unique challenge for experienced hobbyists, but they also have some amazing benefits. 

Some blackwater aquarium benefits include: 

  • They provide a calming, more natural environment for some fish, which can ultimately reduce stress and help them thrive. 
  • These aquariums create ideal water conditions to help some species breed easier. 
  • Blackwater aquarium pH can help reduce heavy metals and high concentrations of calcium, magnesium, sodium, and potassium in the water.
  • Blackwater reduces harmful algae growth. 

The Bottom Line

Overall, creating a blackwater aquarium can be a fun and challenging experience for aquarium hobbyists. 

These tanks come with a range of different benefits and are also attractive to look at. 

Some fish species are a lot less stressed in a blackwater environment which can increase the chances of breeding and can help boost their mood and behavior.

Hopefully this in-depth guide provided you with the necessary tools to set up and maintain a beautiful blackwater aquarium of your own! 

Related:

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Best Betta Food: Ultimate Guide to Feeding Your Betta