Are Indian Almond Leaves Good for Aquarium Fish?

Have you ever seen a stack of large, dried leaves at the fish store and wondered what they are for? Terminalia catappa is the source of Indian almond leaves (IAL), or catappa leaf. This tree, originally from Asia and Oceania, now grows in tropical and semi-tropical areas all over the globe. Its fruit seeds taste similar to almonds, and its leaves are commonly used in herbal teas and traditional medicines.

Fruit and leaves of the Indian almond tree

Dropping a dried catappa leaves into aquarium water will cause it to slow decompose, producing tannins. These are plant-based compounds which gradually lower pH levels and leave the water stained yellow-brown. Many people do not like the tannins naturally produced by leaves and driftwood and use chemical filtration to get rid of the brown tint, but they actually have many uses in the fishkeeping hobby.

What are Catappa Leaves Used For?

If you have sensitive species (like crystal shrimp and certain South American fish) that prefer

Low pH and low water quality

Indian almond leaves slow down the release of tannic acid and humic acid. They take longer to work than pH buffer chemicals, but their gradual effect is sometimes considered “safer” because they are less likely to cause deadly pH swings. They have a detrimental effect on water chemistry so they are not recommended for high pH fish like African Cichlids or other livebearers.

Some soft water fish can live with low pH, but breeding and raising eggs may prove to be more rewarding if the water is made more acidic. Breeders use catappa leaves to raise betta fish (both wild and Betta splendens) and Apistogramma Cichilds. The leaves are able to float for a few days so gouramis or betta fish can create bubble nests beneath them to provide additional support.

Betta Fish in an Aquarium with Tan-Tinted Water

Interestingly, Indian almond leaves are known to have very slight antibacterial and antifungal properties. Tannins are found in nature to help plants resist the attacks of bacteria, fungus and other pathogens. Scientists continue to study their potential use in medicine. Many aquarists use catappa leaves to treat mild illnesses and boost their fish’s immune system. If your betta fish bites his tail constantly, tannins can help speed up his recovery. Some veterans also recommend adding tannin-rich leaves or alder cones when hatching fish eggs to fight off fungal growth.

Microorganisms start to consume the Indian almond leaf as it soaks in water. They quickly reproduce and form a layer of infusoria. This microfauna can be a great food source for tiny shrimp and fry. It is often the only food that is small enough to be eaten by them in their first stages of life. You can soak several leaves in water for up to three weeks if you are going away and don’t have anyone to feed your shrimp colony. You can then drop them into your aquarium to make a long-lasting vacation food.

Blackwater biotope aquarium that imitates a Brazilian forest stream

You can also use lots of catappa and other botanicals to cover your ground if you’re trying to create a South American Biotype or a blackwater aquarium. The darker water makes shiny fish like neon tetras, cardinal tetras, and certain discus really stand out. The tank’s tannins make it more difficult for skittish fish to see, so they feel more at ease. If you add enough Indian almond leaves, the leaf litter can serve as hiding spots for fry or shy bottom dwellers like pygmy corydoras.

How to Use Indian Almond Leaves

If your dried leaves are very dirty or dusty, rinse them in water. Aquarium Co-Op catappa leaves are safe enough to drop directly into your fish tank. They will usually float for about 3-7 days. If this bothers you, weight them down with a rock, or other decoration. Also, you can break the leaf in half to just use part of it or crumble it into smaller pieces to speed up the decomposition process.

Dried catappa leaves ready to be used in aquariums

How many catappa leaves should I use? Start with 1 leaf (approximately 4-7 inches or 10-18 cm long) for every 5-20 gallons of water. If you are making a blackwater tank, use more leaves and soft woods (like Malaysian driftwood and cholla wood) until you achieve the desired color.

Can I boil Indian almond leaf? No. Boiling releases all the tannins, so you won’t be able to reap their benefits. If you don’t like how the leaves look, you can make a catappa extract by boiling one leaf per 0.5 gallons (2 liters) water. (Make sure to use a cheap pot you don’t care about because it may become stained.) Once the liquid has cooled you can add some to the tank until the desired color is achieved. You can add more extract if you need to.

When do I need to replace my catappa leaf? Most leaves only last one to two weeks before they start to fall apart completely. Once you start seeing holes develop in the first leaf, add a second leaf to give it time to start breaking down and releasing tannins.

Caridina cantonensis shrimp chomping on the remains a catappa leaves

Next time you’re thinking of keeping shrimp, breeding soft water fish, or building a blackwater biotope, grab a stack of catappa leaves to get the job done. Aquarium Co-Op leaves come pre-cleaned and ready for use straight out of the box.