Indian Almond Leaves are a natural way to stabilize the water parameters of your fish tank as it releases tannins that are nontoxic and acidic(beneficial acid). It makes the water condition similar to the natural habitat of most fish in the river and other freshwater bodies found in the wild.
This is also used as food for shrimps like Cherry Shrimps and is a great source of nutrients for them. You do not have to feed your shrimp for days if not weeks if you add just one leaf. Many in the fish-keeping hobby use it as a holiday food for shrimp.