Java Fern With Brown Spots - Causes & How to Save

Written by Ivy

Jan 28 2023

Java Fern With Brown Spots - Causes & How to Save

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. They are typically resilient and simple to grow, but on rare occasions they may encounter problems that make them look mushy, brown, and unattractive. Fortunately, most of these problems are simple to fix.

Why Does My java fern Have Brown Spots:

  • Acclimation Period
  • Excessive Lighting
  • Improper Planting
  • New Propagation
  • Nutrient Deficiency
  • Algae Overgrowth

Why is My Java Fern Turning Brown?


When introduced to a fresh tank or environment, java ferns need some time to adjust. It's not unusual for them to almost completely die back before reviving as good as new. Given that java ferns are very disease-resistant, if an established plant is beginning to turn brown, something is probably wrong in its environment. Your plant should fully recover if you make adjustments to elements like lighting, nutrient levels, planting technique, and any overgrowth of blue-green algae.

Acclimation Period

It's likely that the environment in which you add a Java fern to a new tank will be very different from where it was originally growing.

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. (Read More:How to Plant a Java Fern in Aquarium)

As the plant produces new growth that is better suited to its new environment, variations in lighting can also cause burn or dieback.

You might notice that the Java fern's leaves start to look mushy and brown once it is in its new location. There is no immediate reason for concern.

There are valid reasons to leave leaves when possible, even though doing so will improve the appearance overall.

Even leaves that seem to be dying back can add new plantlets to your tank because Java ferns produce new plantlets from the undersides of their leaves.

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

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 a heavily shaded environment by nature, so your tank should reflect that.

It's probably getting too much light if an established plant starts to suddenly turn bleached or brown, especially after switching out a light bulb or moving it to a different spot inside the tank.

To aid in the acclimatization process, move it to a more shaded area or turn down the intensity of your tank lights. Damaged leaves may wither away, but new growth, assuming your lighting isn't too intense, will adapt to your lighting better.


Improper Planting

Java ferns are frequently planted in substrate, which is a common error made by inexperienced aquarists.

Java ferns don't have true roots, in contrast to many aquatic plants. Instead, they attach themselves to abrasive surfaces like rock or driftwood using their hair-like rhizomes.

Java ferns will grow very slowly or not at all if buried in substrate and will eventually start to disappear. Give your fern a suitable surface to anchor on to avoid this.

The rhizomes can be initially fastened to your preferred anchor (submerged wood or rough stone works particularly well) using wire or rubber bands. The artificial attachments can be removed once the rhizomes have established themselves.

New Propagation

Don't be alarmed if you see any dark bumps or spots on the leaves of your Java fern. Your plant is actually multiplying itself, not some strange disease.

Java ferns can reproduce by a process known as apomixis, which effectively allows them to clone themselves! The dark areas on the leaves will eventually sprout plantlets, which are tiny ferns.

This process can initially seem quite alarming because your plant may appear to grow tentacles or other strange growths over night, but it's actually an indication that your plant is strong and thriving.

These plantlets can be anchored to other areas of your tank as they mature and begin to produce their own leaves and rhizomes.

You can either wait until the parent leaf dies back and releases the plantlet to find its own anchor and restart the process, or you can clip the leaves from which they are growing to promote this process.

Nutrient Deficiency

Substratum fertilizers are ineffective for Java ferns because they are not grown in substrate like other aquatic plants are. Instead, through their leaves, they primarily obtain their nutrients directly from the water.

Even though they already have a slow rate of growth, a lack of nutrients in the water will make that rate even slower.

Add liquid fertilizer whenever you add or change the water to help your plant recover after being placed in a new environment or to promote the establishment of new plantlets and rhizome anchoring.

If your vivarium or aquarium also houses fish, snails, shrimp, or other small animals, be sure to only use fertilizers or nutrient additives designed for aquarium use! Fertilizers made for houseplants in pots can be harmful to these.

Algae Overgrowth

Blue-green algae, also known as cyanobacteria, can be problematic for your Java fern even though it is generally not susceptible to disease. Although it isn't attacking your plant directly, it is vying for vital nutrients.

Reduce the amount of light your tank receives and increase the size of your water changes to combat cyanobacteria overgrowth. Additionally, you should manually remove the cyanobacteria biofilm to lessen its effects. Although it won't likely completely disappear, keeping it under control will give your plant the head start it needs to flourish.


Frequently Asked Questions About Java Ferns

What Fish Pair Well With Java Fern?

Practically any freshwater fish can be paired with Java fern because it is robust and hardy. However, Java ferns are much more resistant to being torn apart than delicate aquatic plants, making them a good choice even for these tank mates. Large or aggressive fish may still cause some damage to the leaves.

Can Java Fern Be Grown Entirely Out of Water?

I guess that's the answer. While submersion is not necessary for your Java fern to survive, it does need a very wet and humid environment, so a pot on a windowsill is not going to cut it. But it can still be grown in semi-aquatic environments like riparia and paludaria if it is not planted completely submerged in an aquarium.


Java fern grows slowly, and if it isn't receiving enough nutrients, it may also take a while to die. A nutrient deficiency may be the cause of your java plant losing leaves, developing brown or yellow leaves, having many pinholes in its leaves, producing numerous plantlets from its leaves, or ceasing to produce new leaves.