As with Indian Almond Bark, if your fish comes from a habitat where Indian Almond leaves and other plant debris regularly falls into the water and decompose, your fish will be happier in that environment so trying to mimic it in your aquariums is strongly recommended. Leaves and bark that fall into the water release many different compounds, from dyes to trace minerals, and animals living in the water adapt to having all those different compounds readily available. If your fish comes from the type of environment described above, Catechu Bark is one way of simulating black water condition which is the natural environment for most tropical fish.

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Like Indian Almond Bark, Catechu Bark is high in natural tannins which accounts for its astringent effect and has been proved to harden the scales of bettas as well has sharpening their teeth. Acacia Catechu is also known as cachou, cutch, cashoo, Terra Japonica, khoyer or Japan earth). Catechu Bark is used in Thailand and around the world by betta breeders/keepers that like to fight their fish.

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Making your own Catechu Bark extract is pretty much straight forward:

1st you need a bag of Bettawan Catechu Bark (Acacia Catechu).
 
Next you need a pot big enough to hold at least 1 gallon of water, but the bigger the pot the more extract you will produce. Put 25g - 75g of Bettawan Catechu Bark for each gallon of water inside the pot. 
 
Fill the pot with clean water.
 
Let the Catechu Bark soak in the water for 24 hours. It's best to put some type of weight on top of the bark to stop it floating. The following day boil the pot of Catechu Bark for 15 - 20 minutes. Put to one side and let it cool and stew for another 24 hours. The next day boil the pot again for 10 - 15 minutes.
 
Once the water as cooled you will notice that the water is brown with a very strong fragrance. Filter the Catechu Bark extract through a coffee paper filter or again an old pair of tights. This is to stop any undesirable matter getting into the Catechu extract.
 
The Catechu Bark extract can now be poured into plastic or glass bottles, sealed and stored in fridge or somewhere dark and cool. Recommended Dosage : 1 ounce for 1 gallon of water.