Here is a brief but accurate article on Almond Leave's found and first posted by L-Number Mad.....
Thanks again L-Number.

Scientific Name: Terminalia Catappa Leaves
Common Name: Indian Almond Leaves, Tropical Almond Leaves, Sweet Almond Leaves, Wild Almond Leaves, Sea Almond Leaves, Catappa Leaves, Java Almond Leaves, Ketapang Leaves.

Description:
Terminalia catappa is a large tropical tree in the Family Combretaceae. The tree's origin is controversial, and could have been India, Malay peninsula, or New Guinea. Common names include Indian almond, Bengal almond, Singapore almond , Malabar almond, Tropical almond, Sea almond, and Umbrella tree.

It grows to 35 m tall, with an upright, symmetrical crown and horizontal branches. As the tree gets older, its crown becomes more flattened to form a spreading, vase shape. The leaves are large, 15-25 cm long and 10-14 cm broad, ovoid, glossy dark green and leathery. They are dry-season deciduous; before falling, they turn pinkish-reddish or yellow-brown, due to pigments such as violaxanthin, lutein, and zeaxanthin.

The flowers are monoecious, with distinct male and female flowers on the same tree. Both are 1 cm diameter, white to greenish, inconspicuous with no petals; they are produced on axillary or terminal spikes. The fruit is a drupe 5-7 cm long and 3-5.5 cm broad, green at first, then yellow and finally red when ripe, containing a single seed. (Ref: http://en.wikipedia.org)

Aquarium Use:
Now this is where we shall start. You will discover that a lot of betta enthusiasts often use Indian almond leaves and actually rave for its benefits. The main reason is that their antibacterial properties minimize the chances of bacterial infections, improve health, stimulate the natural environment of fish who hail from soft, acidic waters, stimulate breeding conditions and harden scales in which case as mentioned before does minimize skin diseases and pathogens resulting in bacterial infections that dwell on the epidermis of the fish.

The leaves are often harvested in many Asian countries hence the controversial name originating from various countries. These are considered organic and for aquarium use, they should be free from pollutants and chemicals that could kill the fish.

Like driftwoods and peat, they release heavy amounts of tannic acids. You may not like the looks of yellow water but your fish will naturally benefit from its use. The tannic acids will considerably lower the pH level depending on the hardness levels. Allow one large leaf of 8-10 inches per 10 gallons although I admittedly do not follow what is often recommended as I really like the idea of having a leaf litter in my aquaria no matter the size. Removal of tannic acids is done by either use of activated carbon or doing plenty of water changes.

and there is another option if you dont fancy having the leaves in your tank you can purchase a product called tetra aqua black water extract, it contains tanic acids extracted from almond leaves