Java fern originates from various locations in Asia and has been a long time staple in the hobby. It grows emersed in damp forests, but can also be found completely submerged in some locations. Java fern is a rhizome plant that grows dark green leaves along a creeping rhizome. As there are many varietals of this plant, the leaves may come in a range of lengths and pinnate forms. The most common variant has leaves the length the size of a hand with width about an inch. Its leaves has unique hammered patterning upon close inspection.
Some common variants of Java fern/Microsorum pteropus:
Microsorum pteropus 'needle leaf' - Thin (1-2cm), but longer leaves (up to 30cm)
Microsorum pteropus 'Philipine' - Smaller varietal, shorter leaves around palm length
Microsorum pteropus 'short narrow leaf' - Smaller, more compact varietal
Microsorum pteropus 'orange' - Orange tips in younger leaves
Microsorum pteropus 'Trident' - Leaves have 2 to 5 lobes on each side
Microsorum pteropus 'Thors hammer' - Split end leaves
Microsorum pteropus 'Windelov' - 10 to 20cm, tip splits into many lobes
Microsorum pteropus 'Trident' has lobed leaves.
Java ferns are one of the hardiest plants in the hobby, tolerant of low light and a wide range of water conditions. As it does not need to be planted onto the substrate to grow well - it can be attached to hardscape so that it can be repositioned easily. It can be attached to rocks or wood using string, zip-ties or superglue. If using super glue, gel type super glue (ethyl cyanoacrylate) is easier to work with. These plants can also be glued directly onto hardscape underwater - apply the glue to the rhizome or root mass, then press against the hardscape and hold for around 15 seconds till it adheres. Over time the root mass will attach to the hardscape naturally.
However, contrary to popular literature, it can also be grown (planted) on the substrate, as long as the rhizome itself is not buried. Its roots can and will draw nutrients from soil substrates.
In most fish tanks, it will grow and propagate on its own without special care - drawing available nutrients from the water (nutrients that come with tap water, or fish waste by-products). In some tanks, the lack of critical nutrients cause blackening and deterioration in the long run. Due to its slow growing nature, it will not show signs of nutrient deficiencies till many weeks later. Regularly dosing a comprehensive liquid nutrient fertilizer into the tank water ensures long term health.
Similar to many other plants, Java fern prefers some flow. However, as a slower grower, it can be more vulnerable to BBA if placed in the path of too strong or overly turbulent flow. If you observe that Java ferns in the path of flow are the only ones getting BBA attached to them, consider moving their position or changing the flow pattern in the tank to be more gentle.
Java fern is popular for low tech/non-CO2 injected tanks as it grows well even without carbon dioxide injection or power lights. It grows fast and thicker, with healthier leaves when CO2 injection is provided.
Java fern naturally spawn daughter plants on matured leaves as long as growth conditions are favourable. These baby plantlets can be detached and planted elsewhere as soon as they reach suitable size (about an inch or so).
Longer rhizomes can be divided using scissors or by hand. Make sure to leave a few healthy leaves on each segment of rhizome.