How to Grow and Care for the Finicky Java Fern

Primarily used in aquariums as a decoration, Java ferns are one of the easiest plants for aquarists to grow. This tiny fern provides a good hiding place for fish and mimics their natural habitat. Known as Microsorum Pteropus, it’s found in China, Malaysia, and Taiwan. The Java fern naturally grows in roots and rocks along rivers and waterfalls. Common Java Ferns used in aquariums include the Needle Leaf, Narrow Leaf, Lance Leaf and Windelov.

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What You Should Know about Java Fern

Java fern doesn’t grow in soil or water. It grows only when attached to driftwood or rocks in an aquarium. Some pet stores sell Java ferns already connected to a piece of driftwood. It takes awhile for Java fern to grow after it’s planted, but once it does, it fans out to make your aquarium look more attractive.

Java fern

Photo by ictheostega licensed under CC-BY 2.0

Java fern has green rhizomes, and it’s a striking addition to any 10-gallon or more freshwater planted aquarium, perfect if you have cichlids or South American fish. Even goldfish or other plant-eating fish leave Java ferns alone. Your water pH should be 6.0 to 7.5., with an alkalinity of 3-8 dKH (aka carbonate hardness). And it does well without carbon dioxide.

If you see black lines through the leaves, your plant’s not in trouble. Java ferns have black veins running through them. You also might occasionally notice black bumps, which grow new leaves.

Java fern is one of the easiest to use and most in-demand aquarium plants. Learn more tips and tricks to making your aquarium look good with Java fern from Jacob Castro in this video “Jacob’s Plant Guide: Java Fern” from the Jacob’s Aquarium YouTube Channel

Planting and Replanting Java Fern in the Aquarium

Plant Java fern alone or with groups of other Java fern and other plants. These delicate ferns add a pleasant look to the center of the tank when planted with other types of aquatic plants, or when laced around gravel and aquarium decorations.

Moving or replanting those ferns stunts growth for awhile, but in a few weeks new plants may grow up to six inches wide and a foot tall. Java fern grows in tanks as small as ten gallons and up to 55 gallons or more, with soft to moderate water and a temperature of 72-82 degrees F. If water is clean you won’t need to add fertilizer.

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When planting Java fern, you’re not planting or attaching them to soil or a substrate. If you do bury roots in substrate, the fern absorbs nutrients, and the plant will grow slowly or die. Java fern’s a sturdy plant, and it may survive for a few weeks in gravel or soil, but for the long-term, you should attach it to rock or wood.

Attach Java fern plants or plantlets to rocks or wood pieces. Tie roots of the plant with threads or zip ties to keep them firmly attached. Threads dissolve over time, but you need to remove zip ties when roots grow and secure to the rocks.

Mike from Mass Aquariums explains the correct way to attach fern in the video, “Java Fern: How to plant it or not” on the Mass Aquariums YouTube Video Channel

Place Java fern in the middle or back of your fish tank. Large Java ferns or too many separate plants may obscure fish and other decorations if the plants bloom in the front of the tank.

Lighting Java Fern

Aquarists differ on whether Java Fern needs bright or dim light.

Intense light may burn leaves and result in brown or transparent spots which you’ll need to prune.

Reduce brightness with small incandescent bulbs or softer fluorescent ones. Java fern is one of the best plants for a low-light aquarium.

The Java fern needs 1.5 watts of light for each gallon of water, and 5000-7000 K bulbs work efficiently on most tanks.

Java fern will survive in brackish water. It’s a freshwater aquarium plant, but can stand a bit of salt, up to a water salinity of 1.009.

Java fern grows adventitious, or random plantlets on older leaves. You can remove and replant these plantlets anywhere in your tank. Cut them with sharp, sterilized scissors, then tie them to rocks or wood with thread.

In low-tech and low-light aquarium environments, the Java fern expands into a fan shape and randomly create release new plantlets.

You won’t need to worry about your fish eating the Java fern. It has a bitter taste that even herbivores avoid.

Problems with Java Fern

If you’re not noticing any growth in your newly planted Java fern after a few weeks or months, your water may not carry enough nutrients. Use liquid fertilizer according to label directions until plants start to grow again. The fertilizer you choose should contain iron, which keeps the ferns green. Without enough iron, the Java fern’s leaves will turn drab olive and then black. Adjust the amount once the plants are big enough for your liking. Black spots on leaves indicate nitrogen deficiency.

Brown splotches (just like black bumps) on your fern’s leaves are spores that will eventually turn into new plantlets.

Change 10 % to 25% of your aquarium water every two weeks to prevent excessive accumulation of nutrients and fish waste. Dirty aquarium water harms not only Java fern but other plants and fish.

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Java Fern Melt

Java fern melt occurs when leaves develop large brown spots, turn mushy and rot. (The plant’s rhizomes may remain even though the leaves have rotted.) Java fern melt may be due to one of the following conditions:

  • Low nutrient level

Although Java ferns don’t need a lot of fertilizer to keep them healthy, you may have to add more liquid fertilizer to the plant to restore nutrients.

  • Too much blue-green algae (BGA)

The “algae” that causes melt is a form of bacteria called cyanobacteria, which photosynthesizes like algae. It covers the fern like a thin film and feels slimy to the touch. You can peel and lift it off the fern or other surfaces where it grows. A poor nutrient level causes cyanobacteria to form.

  • Too much light

If you light you tank too brightly, the fern may melt. To resolve this, turn off the aquarium lights for three days and cover with a blanket.

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