Frequently asked questions on aquarium ferns


Many fishkeepers find ferns incredibly useful. Jeremy Gay answers some of your FAQs about these tough and popular plants.

Regular readers will be well aware just how many times the name Java fern crops up in each issue of PFK — and for good reason. Whether you are a plant aficionado or complete beginner, and have a nature aquarium or cichlid tank, ferns can prove incredibly useful.

What exactly are they?

Two main genera of fern are available in the hobby: Microsorum and Bolbitis. The former in the main is represented by Java fern (Microsorum pteropus) and is part of a fern mega-family containing 1,000 species. Most are epiphytes, meaning that they grow on a surface like rocks or wood instead of in the soil.

They are most commonly found in particularly wet environments, like rainforests, and our Java fern also grows out of the water in the wild rather than beneath it, not how we keep them.

Where are these ferns from?

As the name suggests, Java fern is from South-East Asia, where it is quite widespread. Bolbitis heudelotii (pictured above) has the common names of African fern or Congo water fern and comes from the wet areas of the Congo rainforest in West Africa.

What water conditions do these ferns need?

They are incredibly hardy, leading to widespread popularity. In nature they grow out of the water in shaded, tropical, moist conditions, though in the aquarium will grow fully submerged in soft or hard water, temperate or tropical.

They are often recommended even for brackish tanks, though it’s more likely that they just take a long time to die in salty conditions, rather than actually thriving.

Grow them in soft water which has reasonable water flow, a comprehensive liquid fertiliser and CO2 fertilisation.

What type of lighting do ferns need?

Ferns the world over are known for preferring shade and these are no different. In Singapore plant farms, Java fern and Bolbitis are actually grown under thick shading material to prevent exposure to strong light.

In the aquarium both types will readily adapt to strong light, however, although they don’t need it. Anything from one T8 fluorescent tube upwards will be fine.

Who will benefit most from keeping them?

If you keep fish indoors in freshwater, you probably qualify as a potential for Java fern (pictured above). It’s used by goldfish keepers, cichlid keepers, plant growers and Discus owners, as with plant-eating fish the tough leaves are usually left as they seem largely unappealing and inedible.

As it grows on a rock it can be lifted and vacuumed underneath, which is particularly appealing to owners of messy fish. Because of its hardiness and tolerance of low light it also appeals to oddball keepers. It looks great and provides an instantly natural look

Where do I plant them?

On average both Java fern, its variants and Bolbitis grow to around 30cm/12” high and 30cm/12” in diameter. Because of this shape they are usually placed in the midground and make eyecatching specimen plants in their own right.

As they grow on rocks and wood they can contribute to some particularly interesting aquascapes, growing on protruding branches or even vertical rock walls.

How do I fix them on wood?

Buy a pot of any fern and choose a suitable rock or piece of wood. Rough surfaces, like that of lava rock, make for a better anchorage than smooth pebbles.

Remove the fern from the pot and tease away the rockwool growing medium from the roots. Then hold it to the rock or wood while you tie it in place with loops of fishing line. Knot the line and you are done.

Over the next few months the fern will attach to the surface of its own accord. It will grow over the fishing line or you can cut if off. That’s your choice.

How do I fertilise them?

Growing off the bottom of the aquarium, substrate fertilisers will be useless. Instead use an all-in-one liquid fertiliser daily and CO2 diffused into the water.

How do I propagate them?

It’s easy as you can simply prize apart or cut the plants rhizome — fleshy root — to produce several plants or, in the case of Java fern, it propagates its own daughter plants on the undersides of its leaves. These can then be pulled off when just a couple of inches long and be attached to a new surface.

How much are they?

Ferns are slow growing when compared to stem plants like Hygrophila, so that is often reflected in their price. Expect to pay upwards of £3.50 for a basic Java fern in a 5cm/2” diameter pot and more for Bolbitis or rarer Java fern cultivars such as 'Philippine' (pictured above).

Plants sold growing on wood or rocks are typically upwards of £15, depending on size and mother plants — very large specimens — may be upwards of £30.

Avoid 'bunches' of Java fern as these are often just leaf cuttings tied together and missing the all-important rhizome.

What’s available out there?

The original Java fern has been in the hobby for a long time and has proved highly variable. This has resulted in many cultivars of the original Microsorum pteropus, including Narrow fern, Needle fern, Trident fern and Tropica’s ‘Windelov’ (pictured above). There are then another 50 species in the genus Microsorum, though few, if any, are in the hobby.

Bolbitis is also a much larger genus than you may have thought with more than 60 species, though, of those, B. heudelotii is the most popular by far with the asian B. heteroclita more rarely available.

Where can I get them?

Virtually any aquatic shop or website will sell Java fern, though deal with better aquatic shops and mail order plant sellers if you want rarer varieties. New varieties are being released all the time, so expect more in the future.

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