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How To Treat Java Fern Black Spots Quickly!

Java fern is one of the most commonly used aquatic plants within the fish keeping hobby and with the popularity of aquascaping taking off right now and java fern being a popular option with that too, a number of people are reaching out with various questions about caring for the java fern in their tanks.

Thankfully, java fern is one of the easier aquatic plants to care for so there really are not that many problems that people can have with the plant but one of the common issues that we see time and time again is java fern black spots and people looking to treat them on their plants.

Black spots on a java fern do not always indicate that there is a problem with the plant, as the plant will usually develop black spots prior to sprouting new buds with this being totally natural.

In less common cases, black spots on a java fern can also indicate that there are problems with your light intensity, nutrition levels in your tank, or water parameters though.

As we covered in our article on why your java fern is not growing, the majority of the problems that we see people having with their java fern are usually very easy to treat and the same is true for java fern black spots.

The majority of our readers who are having black spots on their plant due to problems should easily be able to fix the issue even if they are brand new to the fish keeping hobby.

Is It Normal For Java Fern To Have Black Spots?

In most cases, black spots on java fern are totally normal and natural with the plant developing black spots as it creates new buds.

Although this can appear to be a potential problem with the plant at first, within a week or two, you should notice a new bud developing and growing on the plant from the area of the black spot.

If you don’t notice a new bud forming from the area on your java fern where the black spot is after two weeks then there is a good chance that there is a problem with the plant that needs to be investigated and corrected.

It does tend to be far rarer that a java fern will develop black spots due to having problems though as the plant is surprisingly hardy and very beginner friendly.

This makes it an excellent option for most people who are new to the fish keeping hobby and want a live plant in their tank that is forgiving and often not affected by many of the common mistakes that we see people new to fish keeping make time and time again.

Still, we doubt that this will stop the constant stream of questions that we see each month from people who are worried about the black spots on their java fern though as its only natural to worry about a potential problem in your tank.

What Causes Black Spots On My Java Fern?

The most common cause of black spots on java fern is due to new buds forming on the plant with their initial development resulting in a small black spot in the area that the bud will sprout from.

Less common but more problematic reasons that you may have black spots on your java fern include problems with light intensity, nutritional levels in your tank, and water parameters.

It is usually very easy to work out if the issue is due to having poor water parameters in your aquarium as you will can test your aquarium water with a decent water test kit to get a quick and easy indication of any potential problems with your tank.

You can also use a aquarium CO2 checker to quickly and easily check the CO2 levels in your tank but this will usually not result in problems with your java fern developing black spots anyway.

Nutritional levels in your tank can often be low if you do too many water changes or change too much of your aquarium’s water too frequently.

When it comes to problems with light intensity burning your java fern to leave black or brown burn marks this can be difficult to confirm.

This is due to cheap lighting units having inaccurate intensity dials and many people who set their lighting unit to a suitable intensity but use a cheaper unit can commonly end up burning their java fern.

How Do I Get Rid Of Black Spots On My Java Fern?

If you are having problems with your java fern developing black spots then you can usually correct the problem by adjusting your light intensity, increasing the amount of nutrients in your aquarium or by fixing any problems that you are having with your water parameters.

All are usually very easy to do and once the problem has been corrected, the black or brown spots on your java fern should start to fade within a week.

Thankfully, two of these problems are very easy to correct as water changes can often be enough to correct problems with some water parameters issues that may result in black spots.

If the issue is due to lighting intensity burning your java fern then you may be able to correct the issue by intentionally tweaking the control dial on your lighting unit but on the cheaper units with inaccurate control dials this really can take more time than its worth so it is usually better to just get a new lighting unit.

The tricky problem is often when nutrient levels in your tank are too low resulting in your java fern developing a number of black spots in quick succession.

You are able to use various types of aquarium fertilizer to quickly increase the nutrition in your tank for your java fern but the alternative methods of using none commercial ways to increase nutritional levels can be problematic and may cause problems with your overall water parameters in your tank.

Will Black Spots On My Java Fern Spread To Other Plants?

In many cases, black spots on your java fern is not an indication of a disease that can spread to the other plants in your aquarium and is usually an issue specific to your java fern.

If the black spots on your java fern are due to natural causes or problems in your aquarium, it is unlikely that they will end up causing problems for your other plants.

Just be mindful of the other types of plant that you keep in your aquarium though as issues such as problems with your light intensity causing spots on your java fern can also be a problem for many other plants that require the same lighting intensity too.

Issues with nutritional levels in an aquarium that cause problems with your plants are usually tank wide too due to all plants requiring nutrition to grow at a healthy rate.


That brings our article going over what causes java fern black spots as well as how you are able to treat them if the spots are due to a problem in your aquarium. Thankfully though, the vast majority of the black spots that people see on their java fern is usually nothing more than new buds emerging from the plant and this is totally natural and to be expected and is actually a sign of a healthy plant.