Betta fish is also known as Siamese fighting fish (Betta splendens) found in freshwater and native to South-East Asia.
Aquarists who keep this fish will use Daun Ketapang (Indian Almond leave, Terminalia catappa) in the water when their fish is sick or lethargic. The dried leave are added to the water, where they will lower its pH and infuse the water with beneficial chemicals. One major chemical component is tannic acid and tannins.
The Ketapang is useful to treat fish skin ailment. The antimicrobial tannin kills bacteria, fungus, and viruses. It is better alternative to the fish antibiotics (ref. 2)
How to make almond leaf extract? The tannin and other phytochemicals are water soluble. You can increase the chemical release by pouring hot water over the dry leave and incubate overnight until the water changes colour. Keep the solution chilled for months.
Tannin is a non-toxic phenol that function as crosslinking agent (ref. 3). It is used to agglutinate microbes in order to inactivate them. Its crosslinking property is beneficial in wound healing (ref. 4)
Tannin has been used in leather-making industry where curing involves chemical crosslinking afforded by adding tannin to the leather (ref. 5).
- Where to find Ketapang leaf (aka Indian Almond Leaf) (https://bettaboy.wordpress.com/2017/09/11/where-to-find-ketapang-leaf-aka-indian-almond-leaf/)
- Indian Almond Leaves: Keeping your fish happy, naturally, 7 Apr 2021 (https://fishlab.com/indian-almond-leaves/)
- Effect of tannic acid as crosslinking agent on fish skin gelatin-silver nanocomposite film (https://www.sciencedirect.com/science/article/abs/pii/S2214289418300747)
- The use of tannins in the local treatment of burn wounds – a pilot study (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3346037/)
- Tanning (leather) (https://en.m.wikipedia.org/wiki/Tanning_(leather))