Indian almond leaves (also known as Catappa leaves or Ketapang leaves) are widely used in the aquarium hobby, especially for fish from soft water habitats such as those found in Southeast Asia and South America. Here are some key points about Indian almond leaves:

1. Natural Habitat: Indian almond leaves come from the Terminalia catappa tree, which is native to Southeast Asia. In the wild, these leaves fall into water bodies and release beneficial compounds.

2. Benefits: 

   - Tannins: When placed in water, Indian almond leaves release tannins that can lower the pH slightly and create a natural tint, similar to blackwater habitats. This can be beneficial for fish that prefer softer, slightly acidic water conditions.

   - Antibacterial and Antifungal Properties: Indian almond leaves are known to contain substances that have antimicrobial properties. This can help prevent bacterial and fungal infections in fish.

   - Stress Reduction: The presence of tannins and other compounds in the water may help reduce stress in fish, promoting overall health and well-being.

   - Food Source: As the leaves break down, they can provide a supplemental food source for small invertebrates and fry.

3. Use in Aquariums: 

   - Indian almond leaves are typically added to the aquarium after rinsing them to remove dust and dirt. 

   - They can be placed directly in the tank or steeped in water to create an extract that can be added to the aquarium.

   - Depending on the size of your aquarium and the desired effect, one or two leaves per 15-20 gallons (55-75 liters) of water is a common recommendation.

4. Duration: Indian almond leaves will gradually break down over time, releasing tannins and other beneficial compounds into the water. Depending on water parameters and fish load, leaves may last anywhere from a few weeks to several weeks before needing replacement.

5. Compatibility: Indian almond leaves are generally safe for use with most freshwater fish, shrimp, and plants. However, it's always a good idea to monitor water parameters when introducing any new element to the aquarium.

Overall, Indian almond leaves are valued not only for their aesthetic benefits in creating a natural-looking environment but also for their potential health benefits for aquarium inhabitants.