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Why is my Java Fern turning brown? – Mystery SOLVED

Why is my Java Fern turning brown? – Mystery SOLVED

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Java ferns are a beautiful addition to just about any freshwater aquarium or aquatic vivarium since they can grow either partially or fully immersed in water. While they’re generally hardy and easy to grow, occasionally they can experience issues that leave them looking mushy, brown, and unappealing. Thankfully, most of these issues are easily resolved!


Why is my Java fern turning brown?

Java ferns require a period of adjustment when added to a new tank or environment. It’s not uncommon for them to die back almost completely before springing back good as new. If an established plant is starting to turn brown, something is likely off in its environment, as Java ferns are very resistant to disease. Adjusting factors such as lighting, nutrient levels, or planting method, and removing any overgrowth of blue-green algae, should allow your plant to recover completely.


Acclimation Period

When you add a Java fern to a new tank, chances are the environment will be considerably different from its original growing space.

Many Java ferns grown for cultivation are grown “emersed,” or only partially submerged, so the transfer to a fully aquatic environment takes some getting used to.

Differences in lighting can also trigger burn or die back as the plant produces new growth that’s better suited to its new environment.

Once placed in its new space, you may notice the Java fern’s leaves growing brown and mushy looking. This is not cause for immediate alarm.

While you can remove unsightly leaves to improve the overall appearance, there are good reasons to leave them when possible.

Java ferns produce new plantlets from the undersides of their leaves, and even leaves that appear to be dying back can add new plantlets to your tank.

A small amount of decomposing plant matter also adds nutrients to your tank that your Java fern can use to help bounce back.


Excessive Lighting

Java ferns are tropical plants found low on the rainforest floor—often in flood zones, which explains their ability to grow either partially or completely submerged.

This is naturally a highly shaded environment, which should be replicated in your tank.

If you notice an established plant suddenly turning bleached or brown, especially after changing a light bulb or moving it to a new location within the tank, it’s probably getting too much light.

Shift it to a shadier location, or reduce the amount of time your tank lights are on to help it acclimate. Damaged leaves may die back, but new growth will be better acclimated to your lighting, provided it isn’t excessive.


Improper Planting

One mistake many novice aquarists make when planting Java ferns is planting them in substrate.

Unlike many aquatic plants, Java ferns don’t have true roots. Instead, they anchor themselves, using their hair-like rhizomes, to rough surfaces like driftwood or rock.

If buried in substrate, Java ferns will grow very slowly or not at all, and will eventually begin to die off. To prevent this, provide your fern with an appropriate surface on which to anchor.

You can use wire or rubber bands to initially attach the rhizomes to your chosen anchor (submerged wood or rough stone works particularly well). In time, the rhizomes will take hold and you’ll be able to remove the artificial attachments.



If you’re noticing dark bumps or spots on your Java fern’s leaves, don’t worry! It’s not some strange disease, but rather your plant propagating itself.

Java ferns reproduce using a process called apomixis, which means they’re essentially capable of cloning themselves! Miniature ferns, called plantlets, will spring up from those dark spots on the leaves.

This process can look quite concerning at first, as your plant may seem to develop tentacles or strange growths overnight, but it’s actually a sign that your plant is healthy and thriving.

As these plantlets develop, they will start to grow their own leaves and rhizomes and can be anchored elsewhere in your tank.

You can either clip the leaves from which they’re growing to encourage this process, or wait until the parent leaf dies back and releases the plantlet to find its own anchor and start the process again.



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Nutrient Deficiency

Since Java ferns aren’t planted in substrate like other aquatic plants, substrate fertilizers are not effective for them. Instead, they gather most of their nutrients directly from the water through their leaves.

They’re a slow-growing plant already, but too few nutrients in the water will slow the process even more.

To help your plant bounce back after being added to a new environment, or encourage new plantlets and rhizome anchoring, add liquid fertilizer whenever you add or change the water.

Make sure to only use fertilizers or nutrient additives appropriate for aquarium use, especially if your vivarium or aquarium also contains fish, snails, shrimps, or other little critters! These can be harmed by fertilizers designed for use with potted houseplants.


Algae Overgrowth

Though not susceptible to disease generally, the one thing that can cause some problems for your Java fern is blue-green algae, or cyanobacteria. While it’s not actually attacking your plant, it is competing for critical nutrients.

To deal with cyanobacteria overgrowth, decrease the amount of light your tank is getting and increase the size of your water changes. You’ll also want to manually remove the biofilm of cyanobacteria to reduce its impact. It’s not likely to vanish completely, but keeping it in check will give your plant the head start it needs to thrive.


Frequently asked questions about Java Ferns


What fish pair well with Java fern?

Since Java fern is tough and sturdy, just about any freshwater fish can be paired with it. Large or aggressive fish may do some damage to the leaves, but Java ferns are much more resistant to shredding than delicate aquatic plants, so they’re a good choice even for these tank mates.


Can Java fern be grown entirely out of water?

The answer is sort of. While submersion is not critical for your Java fern to survive, it does require a very wet and humid environment, which means that a pot on a windowsill is not going to work. If it’s not planted fully submerged in an aquarium, however, it can still be grown in semi-aquatic set ups like riparia and paludaria.