The blackwater aquarium aims to replicate the conditions found in blackwater biotope.
Blackwater aquariums are created from a mixture of leaf litter and plants, creating a tinted water effect. The process is similar to the brewing of tea, where the properties of dried tea leaves are infused with water.
Tannins [are] a yellowish or brownish bitter-tasting organic substance present in some galls, barks, and other plant tissues, consisting of derivatives of gallic acid, used in leather production and ink manufacture.Oxford
Examples of fish native to blackwater habitats include Betta and Tetra fish.
Most tropical aquarium fish originate from blackwater habitats. Oftentimes, fish that come from both the Amazon basin and Southeast Asia, from two separate continents, will have similar care requirements because they have adapted to similar habitats.
As mentioned earlier, the blackwater aquarium is brewed with dried and rotting plant matter that enters the water. This yellow color is created by tannins that are released into the water when the dried leaves or driftwood start to disintegrate.
Tannins are responsible for not just the change in color within the aquarium, but also will lower the pH and soften the water. The pH level of blackwater aquariums typically ranges between 5.5-6.5 however, in some cases, they can be as low as 4.5.
In the wild, blackwater habitats provide shelter and nutrition for many species of fish. Leaf litter (a component of the blackwater habitat), starts to rot over time creating opportunities for rotifer colonies (microscopic invertebrates) to grow, from which fish fry can then feed on.
The leaf litter also provides many hiding areas for fry and smaller species of fish, providing shelter against predators. Thus creating a symbiotic relationship between the fish and its environment.
Pretty cool, eh?
Now, you’re wondering how you can create blackwater.
There are a few ways to create a blackwater environment in the aquarium.
I generally do not recommend this method however it is the simplest and easiest method to obtain a blackwater aquarium.
There is a variety of blackwater concentrates that can be used in an aquarium. For example, the Betta SPA is specially formulated to mimic the parameters found in the natural habitat of betta fish.
1. Blackwater extracts
Just a few drops into your tank and you can expect to see that tinted yellow glow. However as convenient as it may be, this method should be used carefully, since it can drastically and suddenly change the biochemistry of an aquarium.
Generally, it is recommended that fishkeepers gradually insert the extracts in their aquarium.
2. Indian almond leaf
This method of creating blackwater is the preferred method as it a more natural way of introducing blackwater.
Also known as ‘ketapang’ or ‘cattapa’ leaves, the Indian almond leaf is no stranger to the aquarium trade. This leaf comes from the Indian almond tree and is native to Asia, Australia, and Africa.
For years, hobbyists have been using this leaf to create blackwater systems for a few reasons. It is said that the tannins released by the indian almond leaf have healing properties and is able to prevent fungal growth, some experienced hobbyists swear by them.
Some fishes also require blackwater to breed, as such, adding Indian almond leaves will mimic their natural habitat, encouraging spawning to happen.
The presence of the Indian almond leaf also provides space for fry to hide. This is important as some fishes have the habit of killing or eating their own fry upon hatching, so the addition of the Indian almond leaf also acts as an additional layer of protection.
The Indian almond leaf is also a popular choice because it not only comes with all the above benefits, but it also decomposes slower than most other varieties of leaves, which means the leaves do not need to be replaced as often as another leaf might.
Driftwood is also a common way of introducing tannins into your aquarium. This is the “slow-cook” method.
New hobbyists often don’t realize that driftwood can releases large amounts of tannins. It is also a common misconception in new hobbyists that once the water turns a tinge of yellow, the tank is dirty.
Below are some species of common blackwater fish:
- Neon tetras (Paracheirodon innesi)
- Cardinal tetras (Paracheirodon axelrodi)
- Guppy (Poecilia reticulata)
- Angelfish (Pterophyllum scalare)
- Corydoras Catfish (Corydoras)
- Discus (Symphysodon)
- Dwarf Gourami (Trichogaster lalius)
- Sparkling Gourami (Trichopsis pumilia)
- Cherry Barb (Puntius titteya)
How many leaves should I add to the tank?
Generally, adding these leaves into the tank does not constitute much risk although it does cause the pH to drop slightly. A general rule of thumb would be 10 ketapang leaves for every 5 gallons of water.
But this heavily depends on how pronounced you want the blackwater effect to be in the tank. 10 leaves in a 5-gallon tank will produce a moderate tea colour, and 10 leaves in a 5-gallon tank will make for a dark tea colour. Keep in mind, the more leaves you put into the tank, the faster your pH will drop and the softer your water will be.
When adding the leaves into the tank, you will probably notice them floating. Leave them be and they will sink in about 24hrs.
Do I need to remove the leaves from the tank?
The leaves should be left there until they disintegrate completely because they function as part of the entire ecosystem within your tank. The leaf’s purpose is not just to colour the water, but also to provide macronutrients to the tank’s inhabitants.
Small fishes also will feed on the fish and if you have shrimp, they too will feed on the disintegrating leaves. So do not worry as they will quickly disappear before you know it.
Leaving the leaves in your tank also creates a great aquascape for a more natural aquarium feel.
Where can I buy these leaves?
Unless you live in Asia, Australia, or Africa, chances are that you won’t find these leaves while on your evening stroll.
However, they are now readily available on websites such as eBay and Amazon.