Blackwater Benefits in Aquarium Keeping

Blackwater Benefits in Aquarium Keeping

Many fish kept in the aquarium hobby are favourable of water stained heavily of tannins. These tannins are often induced by hobbyists by adding leaves and other botanicals. Conveniently, they are also available in various bottled extracts and supplements that can easily be added during your weekly maintenance routine.


Benefits include

  • Reduces and Stabilises PH and Ammonia.

Although quite well known are the PH lowering abilities if IAL. What many aquarists are not aware of is that with this ability they can also be used to control ammonia in your aquarium as a result. Below a PH of 7, ammonia(NH3) is present as ammonium(NH4) which is not harmful to fish at all. For this reason, labyrinth breathing fish like Betta are able to not only live in dark tannin-stained water bodies but actually thrive!

  • Can help to lower water hardness.

As Indian almond leaves decompose they release Humic Acid. These acids work against the carbonate hardness(KH) of the water to bring the PH lower, lowering the KH as a result.

  • Acts as an Anti-fungal, Anti-bacterial and Anti-Parasitical agent.

IAL are well known for their anti-fungal properties, fish eggs are less likely to succumb to fungus and injuries are seen to heal quicker due to the lower amounts of bacteria in the water column. In addition, external parasites are inhibited by the addition of the blackwater.

Humic acids and Fulvic acids boost immunity and disease resistance and are also known to be a powerful antioxidant.

  • Promotes breeding behaviour.

Many species of tropical fish breed when water levels are quite low prior to the onset of a wet season. its during this time after a dry spell that there is an abundant amount of leaf litter strewn throughout these small watercourses. At this time the observed tannins are concentrated the most creating the blackwater. These conditions promote the fishes instinct to breed.

  • IAL tannins act as a natural flocculant.

While blackwater appears to be dark tea stained the water is generally void of suspended turbidity. The leaves contain a coagulant that binds to particulate and settles it out of suspension.

  • Provide food for fish fry and shrimp.

As the leaves decay they harbour microorganisms called infusoria and paramecium. These organisms are what many fry and shrimp feed from as their first foods after they hatch.

Indian Almond Leaves

Introducing Tannins into the Aquarium

Indian Almond Leaves

Indian Almond Leaves(IAL) are the leaves from the Terminalia Catappa tree which are native to parts of Southeast Asia. The leaves are harvested once fallen from the tree, cleaned and flattened prior to use.

As demonstrated, in our store we choose to use IAL for the blackwater benefits they provide in our betta aquariums. We soak the leaves in our water change barrel 3 days prior do using for a water change to ensure the leaves have had ample chance release the tannins. Prior to conditioning our water this way we kept them in a filtered system with very mixed results.


In much the same way as Catappa leaves, tannins can also be added to the aquarium via driftwood and bogwood although some woods are more adept at it than others.

Bottled Extracts

As previously mentioned, there are many bottled Indian almond leaf extracts available in the market and all have their merits.

We have used and recommend the use of Continuum Blackwater Extract for larger blackwater aquariums containing Discus, Angelfish and other South American fish. For Bettas we have found Atisons Betta Spa to be the product of choice.


We find our fish to be in better health, have more vibrant colours and exhibit more natural behaviours with the addition of Blackwater Extracts whether from IAL or bottled extracts.

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