Java Fern and Anubias: Plants That Grow on Rock in Strong Flow

Most aquarium plants get uprooted in a river tank. The current washes the gravel away from their roots and they float off. Java fern and anubias solve that problem: they don't go in the gravel at all. They grow on rocks and wood, just like they do in the streams they come from.

The one rule: don't bury the rhizome

Both plants grow from a rhizome, the thick horizontal stem that the leaves and roots come out of. If you bury it in the gravel or sand, it rots. Instead, attach the plant to a rock or a piece of driftwood and let the roots grab on by themselves.

How to attach them

Tie them on. Wrap cotton thread or fishing line around the rhizome and the rock or wood. Snug, not tight enough to cut into it. In a few weeks, the roots grip the surface. Cotton thread rots away by itself; fishing line you can snip off later.

Glue them on. Gel-type super glue (cyanoacrylate) is safe for fish once it sets. Dry the spot on the rock and the rhizome, put a dab of glue on the rock, and press the plant on for 30 seconds. This is the fastest way.

Wedge them in. Tuck the rhizome into a crack between rocks or under a root. Easy, but make sure the current can't pull it out.

Java fern

Java fern (now classified as Leptochilus pteropus) has long, tough, leathery leaves. Fish and most snails leave it alone. Varieties include narrow leaf, needle leaf, "trident" and "windelov," which has frilly leaf tips.

• Light: low to moderate. Strong light can burn it brown or black.
• Growth: slow. It makes baby plants on its leaves, which you can pull off and tie somewhere else.
• Brown or clear patches usually mean too much light or a nutrient shortage, or occasionally that the rhizome got buried.

Anubias

Anubias (usually Anubias barteri and its varieties, like the small "nana" and "petite") has thick, rounded, dark green leaves that are almost indestructible.

• Light: low. It grows slowly, and in strong light its leaves can grow algae spots.
• Growth: very slow, a leaf every week or two.
• Placement: in the shade of a rock or wood, if your light is strong.

In strong current

Both plants are ideal for a river tank. Their leaves are tough enough to handle flow, and once their roots attach they don't wash away. Put them in the moderate-flow parts of the tank, and use them to make the calm pockets fish need behind rocks.

Above the water in a riparium

Here's the riparium bonus: anubias in particular can grow emersed, with its roots in the water and its leaves in the air. Tie it to a rock or wood that sticks out of the water and it will grow slowly in the humid air above the tank. Java fern can grow partly out of water too, as long as the humidity stays high. See our guide to riparium plants with roots in the water for more.

Care

• Liquid fertilizer helps, since they don't feed from the gravel.
• Trim old, damaged leaves at the base.
• Clean the leaves gently if algae builds up, or let a nerite snail or Amano shrimp do it.

Sources (2)

Wikipedia: Leptochilus pteropus (Java fern) · Aquariadise: How to Tie Aquatic Plants to Wood or Rock