How to Plant, Grow, and Care for Java Fern

Those of us who keep aquariums around to enjoy fish swimming around have an unusual outlet for gardening right in front of us. Growing Java fern in our fish tanks is a great way to bring greenery indoors. Besides, your underwater pets will love it!

Deep green in coloration, these aquarium varieties are perfect back-layer plants for a fish tank. A mature Java fern can grow to reach upwards of 13″ tall. The swaying leaves provide cover for your aquatic residents and a splash of color in an otherwise dull tank.

Ready to grow your own underwater jungle? Let’s talk about everything you’ll need to know!

What is Java Fern?

The Java fern is a popular aquatic widely used in freshwater aquariums for its hardiness and leafy appeal. It grows well in various water conditions, making it an excellent choice for beginner and experienced aquarists. These epiphytic plants can attach to surfaces like rocks, driftwood, or other decorations rather than root in a substrate.

Native Area

With a natural habitat originating in Thailand, parts of China, and Malaysia, Leptochilus pteropus, previously Microsorum pteropus is a variable water-loving plant. In the wild, these Java ferns grow both submerged in water and partially above the surface, dwelling in boggy areas or along waterways.

Characteristics

These aquatics consist of three basic parts: a root system, a rhizome, and the leaves.

Tendril-like dark brown roots are used to attach it to its chosen medium. Instead of its root system, the fern absorbs nutrients with these as much as they’re used for simply hanging on. These super-fine, hair-like tendrils do a great job of it.

This rhizome forms the base and absorbs most of its required nutrition from the water around it. Over time, the rhizome will grow to cover whatever object it has grabbed onto, and can easily spread to reach six inches wide.

Leathery, dark-green leaves form the rest of the fern. They vary in shape depending on the origin and growing conditions. Some are narrow-leaf fern varieties, like the needle-leaf fern, and others have a less narrow leaf. The leaves also form the reproductive portion, as they can form spores and develop plantlets directly on the leaf surfaces.

While the length of the leaves is somewhat variable, these often reach 13″ or more in length, so are often used towards the rear of an aquarium.

Varieties

There’s multiple different Java fern types out there. Among these are:

‘Windeløv’

Because of its fine leaf shape, this is sometimes called lace Java fern. Delicate and feathery, the ‘Windeløv’ variety can be used in conjunction with broader-leafed varieties for visual appeal. Due to its finer leaves, this also tends to be shorter.

‘Philippine’

A broad-leaved variety, it is distinctive in that its leaf surfaces appear to be hammered. This variety is quite popular but can be difficult to find.

‘Trident’ 

‘Trident’ has needle-like feathery leaves that sway in the water in an appealing way. This is what a lot of people think of when they think of underwater plants – long, swaying fronds which join together close to the rhizome. Very pretty variety.

‘Narrow’

Slightly wider towards the leaf base than ‘Trident’ is, ‘Narrow’ has a similarly-flowing long and tapered leaf shape. It’s best described as an extremely elongated teardrop shape, and it’s slightly textured in a similar way to the ‘Philippine’ Java fern.

‘Undulata’

‘Undulata’ is an interesting variety in that its leaves tend to be almost the reverse of the shape of the ‘Narrow’ variety’s leaves. Pointed tips widen dramatically on the upper portion of the leaf, then gradually decrease until the leaf vanishes into the rhizome at its base.

How to Grow

Considered among the easiest aquarium varieties to grow, Java fern is a fantastic addition to your planted aquarium. But it’s unlike many other sorts of plants. Let’s go over care conditions for your Java fern and how you can successfully grow it!

Light

Whereas many plants love lots of sunlight, Java fern is actually a low-light variety. Too much light can burn the leaves, causing brown patches to appear. In really severe cases, the leaves can become transparent and begin to dissolve.

A reasonable rule of thumb is to aim for 1.5 watts of soft lighting for each gallon of water in the tank, using small incandescent lights or soft fluorescents. If this still seems to be too much light, consider back-lighting the tank with low-light LEDs and reducing your upper lighting even more.

Water

Java fern is an aquatic that can grow fully submerged in an aquarium, so it’s safe to say that it loves humidity! This holds true whether it’s fully or partially submerged, and its root system and rhizome should be constantly in contact with water for best growth.

When it comes to general java fern care, it will thrive if completely submerged in a fish tank or a pond, although the tips of its leaves can rise over the water’s surface. If too much of the leaf surface is exposed to the air, it may require additional nutrients to sustain itself properly.

Java fern can survive living in brackish, salty water but prefers fresh water. Salinity shouldn’t go above 1.00g, as it may show signs of leaf melt at higher levels of salinity. The pH level of your water should be between 6 and 7.5, as well.

It’s important to change 25% of your aquarium’s water every two weeks to remove excess nutrients or fish waste and keep the water fresh. It also loves oxygenated water, so aquariums with pump systems are ideal. It doesn’t need CO₂ as much as other water types.

Soil

These are epiphytes, like Spanish moss or many bromeliads. They do not require soil at all to live, and, in fact, prefer their roots to be fully exposed and not buried at all.

Generally speaking, the growing medium that is most common for these aquarium ferns is either pieces of wood or large rocks. On occasion, it has been attached to decorative features made for fish tanks. Grow Java fern in a soilless mix or on one of these surfaces.

Loosely secure Java fern on driftwood or rocks with a piece of cotton thread. This keeps the roots in contact with the growing medium until they can develop a firm grip, and the thread will eventually rot away.

Temperature

Temperature-wise, Java ferns love temperatures in the 70-75°F range but can tolerate anything from 60-83°F. The ideal temperature range ensures optimal growth and helps it maintain its vibrant green appearance.

Prolonged exposure to temperatures below 64°F or above 86°F can stress the plant, leading to slower growth or damage to its leaves.

Fertilizer

Aquatics require four basic nutrients to grow: iron, manganese, nitrogen, and phosphorous. Sometimes, additional micronutrients such as copper, zinc, borate, or molybdenum are also necessary.

The fertilizer you’ll want to use is a bit different than a traditional fertilizer. Designed to be safe for fish and ferns, it comes in two different formats: liquid fertilizer and tablet.

Liquid fertilizer may cause some clouding of the water or promote blue-green algae growth if you use too much of it. When in doubt, under-fertilize with liquid fertilizer. Follow the manufacturer’s directions for your tank size. Don’t use a standard liquid plant fertilizer, as it may be risky for your fish.

As an alternative, there are tablet-type aquarium fertilizers. These slow-release capsules are buried in the tank’s substrate and will release their nutrients over a period of time.

It takes some trial and error to determine where to bury the capsule in the tank. While a liquid fish fertilizer immediately spreads throughout the water, tablet varieties don’t always spread over the entire tank’s water supply.

Maintenance

A few things may need to be maintained to ensure that the ferns are healthy and well cared for. Re-positioning may be necessary if they outgrow the space, and pruning can help. Let’s discuss these in more detail:

Repotting

With Java fern, repotting is more like securing and moving. As its roots don’t like being buried, you can instead secure young plantlets to driftwood or rocks with cotton thread.

While doing this, be gentle. Don’t tie down the ferns tightly as it can risk damage to the root structure. Instead, loosely secure the rhizome to the surface with the thread, ensuring that the roots are in contact with the surface. The roots will grab on in time as the thread rots away in the water.

If at all possible, do this process working in a bowl of fresh water. This keeps it moist and the movement of the water helps it to fan out its roots comfortably.

Once secured loosely to their growing medium, you can place them in outdoor shaded ponds or in aquarium tanks. Be sure that these are freshwater locations if at all possible. If using an aquarium, go for a 10-gallon or larger size rather than a small fish bowl so it has room to grow.

Pruning

Occasional light pruning encourages development. Remove larger leaves just above the rhizome to give it more energy for growth. Don’t take too many off; select just one or two of the largest leaves.

Pruning in that fashion will, in time, result in a much larger fern overall, as the rhizome will have enough time to develop a larger base from which to send up leafy growth.

If Java fern melt begins to appear, remove damaged leaves immediately by pruning them off just above the rhizome. See the problems segment below for more information on java fern melt, as well as other ways to halt the damage it causes.

Propagating

The beauty of growing these ferns is that they’re self-propagating. And they do so in a number of different ways.

The tips of Java fern leaves can develop dark bumps. These turn into young plantlets and, in fact, look as though a second one is growing out of the first. When they’re old enough, these plantlets will drop off the leaf tips and float around the tank in search of something to latch onto.

In addition, leaves which are regularly out of water can form spores along their undersides. These spores can be carried via air or water to other surfaces, allowing them to easily spread.

The rhizome of the fern itself will widen over time, increasing the size and the number of leaves that can be actively reproducing. Many growers find themselves with an abundance of young ones in time!

Common Problems

Overall, your aquatic Java fern won’t have many problems. But let’s go over what few may exist.

Growing Problems

Black lines running through the leaves of other plants may be causes of concern, but for Java fern, it’s fairly normal. Java fern can have dark-colored veins inside its leaves depending on which variety it is. They also can form brown or black bumps that will turn into plantlets.

However, if the leaves start turning completely black or a drab olive-green color, they are crying out for more nutrition. To remedy this issue, use aquarium plant fertilizer per the manufacturer’s directions.

Pests

When we think of pests, normally they’re insects. But Java fern doesn’t seem to attract insects. In fact, the only thing that it seems to attract are snails, who seem to like living amongst its leafy greenery.

While snails won’t harm your Java ferns, some tiny forms can be found clinging to store-bought aquatics from time to time. But these snails can pose a problem to the fish in your tank or to other aquatic flora that you may have.

Purchasing a single assassin snail for your tank can remedy snail problems. It will eat the tiny snails and continue to live in your tank, cleaning up leftover fish food and some forms of algae.

Even the fish themselves are not tempted to snack on your ferns. It’s believed that their tough leaf structure makes it unattractive for most fish to nibble on for very long, which means they tend to survive in most aquariums.

Diseases

While not susceptible to most common plant diseases, there is one thing that java fern does suffer from: Java fern melt.

If the leaves start to develop large brown or black spots, turn translucent or mushy, or start to dissolve and rot away into the water, there’s a few different possible causes. Let’s go over those now.

Begin by being sure that you are not suffering from cyanobacteria in the tank. Cyanobacteria, also called blue-green algae, is caused by poor nutrient levels and creates a bacterial film over all surfaces of the fern and other parts of the tank.

If you find cyanobacteria, peel away the filmy bacterial layer from the fern or other parts of the tank. Change out 25-50% of the water in the tank, then fertilize and maintain good nutrition to keep this algae-like bacteria at bay.

Poor nutrition itself can cause melt as well. If you maintain regular feedings, this should prevent this issue.

Finally, excess bright light can cause translucent leaves to melt. If this appears to be happening, prune off damaged leaves, then turn off all the lights (but not the water pump) and cover the aquarium with a blanket or towel to create a completely dark environment.

Leave the lights off for up to three days to allow time to recover.

While melt is not easy to diagnose, ensuring that your water is regularly freshened, that the ferns are fertilized, and that there is no bacterial growth or excess bright light should prevent further outbreaks.

Frequently Asked Questions