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? Indian almond leaves (IAL) or catappa leaves come from Terminalia catappa, a tree that originates from Asia and Oceania but now grows in tropical and subtropical regions all over the world. Its fruit seeds taste similar to almonds, and its leaves are commonly used in herbal teas and traditional medicines.

The Indian almond tree bears fruit and leaves

When you drop a dried catappa leaf into your aquarium water, the leaf begins to slowly decompose and produce tannins, which are plant-based compounds that gradually lower the pH and stain the water with a yellow-brown tint. 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 are a sensitive species (like crystal shrimps and certain South American fish), that may be a preference.

Low pH and low water quality

Indian almond leaves slowly lower pH levels by releasing tannic, humic, and fulvic acid organic compounds. Although they take longer to produce pH buffer chemicals, their gradual effect can be considered safer as they are less likely cause dangerous pH swings. The leaves have a negative impact on water chemistry and are not recommended for use by high-pH fish such as African cichlids or many livebearers.

Although some soft water fish do not require a low pH to live in their natural environment, breeding and raising fry may prove more difficult if the water is 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 are kept in an aquarium that has tannin-tinted water

It is interesting to note that Indian almond leaves have slight antibacterial or antifungal properties. In nature, tannins help to protect plants from attacks by bacteria, fungus, and other pathogens, and scientists continue to research their antimicrobial efficacy for possible use in human medicine. Many aquarists use catappa leaves to treat mild illnesses and boost their fish’s immune system. Tannings can be helpful for betta fish who bite their tails. For fungal growth prevention, experts suggest adding alder cones or tannin-rich leaves to hatch fish eggs.

As the Indian almond leaf soaks in water, microorganisms begin to consume and break it down. They rapidly reproduce and grow into a layer of biofilm and infusoria. This microfauna makes excellent food for shrimp and fry, and can even be the only food they eat in their early years. If you’re planning on leaving town but don’t know anyone who can feed your shrimp colony, soak several leaves in water for three weeks. They will then become slimy and biofilmy. 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. The leaf litter can be used as a hiding place for fry and shy bottom dwellers, such as pygmy corydoras, if you have enough Indian almond leaves.

How to Use Indian Almond Leaves

If the dried leaves are very dusty or dirty, you can gently rinse them in water first, but the catappa leaves sold by Aquarium Co-Op are clean enough that we just drop them directly into the fish tank. They will usually float for about 3-7 days. If this bothers you, weight them down with a rock, or other decoration. You can also cut the leaf in half or break it up into smaller pieces to speed the process.

Dried catappa leaves, ready for use in aquariums

How much catappa should I use? Use one leaf for every 5-20 gallons. You can use more leaves or soft woods, such as cholla and Malaysian driftwood, to achieve the desired color in a blackwater tank.

Do I boil Indian almond leaves for their health benefits? Not because boiling them releases the tannins. Some people prefer to make a catappa herb extract. This is done by boiling one of the leaves for every 0.5 gal (2 liters), of water. (Make sure to use a cheap pot you don’t care about because it may become stained.) After the liquid has cooled down, add a small amount to the tank to achieve the desired color. You can add more extract if you need to.

When should I replace the catappa leaves? Most leaves last about one to two months until they break down completely. Add another leaf to the plant to allow it to break down and release tannins.

Caridina cantonensis shrimp eating the remains of a catappa Leaf

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.