Ferns in the Aquarium


(Unedited version)
Originally appeared in the August 2008 issue of
Tropical Fish Hobbyist Magazine

Ferns are beautiful primitive plants whose fossils date back to over 350 million years. More complicated and better developed than mosses, having developed a vascular system to transport water and nutrients, ferns still use spores to reproduce. Though they have leaves they do not produce flowers unlike the angiosperms which have since come to dominate the plant world.

Traditionally ferns have been grouped with club mosses and horsetails, all primitive vascular plants that produce spores. It was previously believed that these plants were not really that closely related. New molecular evidence places the single genus of horsetails, Equisetum, within the division of ferns.

Ferns have an unusual method of sexual reproduction going through 2 main phases. There are differences and variations but basically the reproduction process goes like this: The gametophyte is small and grows when a spore lands in a suitable place. Though there are different shapes, many ferns gametophytes resemble small hearts, and look similar to liverworts. The gametophyte eventually produces eggs and sperm. When these meet (usually through cross fertilization) they produce what's called a zygote, which eventually grows to become a sporophyte, which is the familiar looking plant that we recognize as a fern. These eventually grow to produce new spores that create a new generation of gametophytes. Spores can often be seen as little black dots under the leaves of ferns.

Sexual reproduction in ferns is somewhat complicated, fortunately you don't need to worry about it. New plants are easily obtained by cutting off portions of rhizomes, through runners or small plants that grow on the edges of mature fern leaves.

Microsorum pteropus

Microsorum are a genus of about 50 different species of fern, most of which are not aquatic, they are sometimes called wort ferns. In the world of aquariums its M. pteropus, the Java Fern, that is clearly the most well known and popular of the aquatic ferns. It comes in a variety of naturally occurring variations and man made cultivars. One of the most lovely and popular is the very lacy Windeløv variety, named for Tropica of Denmark's founder Holger Windeløv. There are also narrow leaved varieties that are often available among others.

Java ferns are generally easy to grow in most aquariums and a good beginner plant They can survive in a variety of water conditions and will tolerate low to high lighting, and are usually happy whether you add CO2 or not. There have even been accounts of some Java ferns living in lightly brackish water. Java ferns are not tasty to most fish so they can often be kept in tanks where other plants become fish salad bars.

Java ferns should not be planted in your substrate. The rhizomes, which is the stem like part that roots and leaves grow from, should be tied to wood or rocks in the aquarium. You can use fishing line or sewing thread. Some people even staple plants to aquarium wood. The plants may be placed at the substrate but the rhizome should not be buried, as it will most likely rot and die.

Java ferns often propagate quite easily in the aquarium. Small plants form on the edges of mature leaves and these can be removed and placed elsewhere in the aquarium or given to friends. You can also cut sections of the rhizome off the main plants, and these will also happily keep growing as a new plant.

Bolbitis heudelotii

Bolbitis is another genus of ferns with over 80 species, which are almost all terrestrial. Bolbitis heudelotii however, is aquatic and can often be found offered for the aquarium. Commonly called African fern, this is a very attractive plant. Similar to the Java fern, African ferns grow leaves and roots along the rhizome which can be cut for propagation.

Though somewhat similar to the Java fern B. heudelotii, is usually a more difficult and demanding plant. It prefers soft, clean, slightly acidic water and will usually benefit from the addition of CO2. My tap water is far from acidic and moderately hard, and so I have only been able to grow Bolbitis with the addition of CO2. It grows naturally in flowing water and water movement in the aquarium may help encourage growth. If it does like the conditions in your tank and water it can grow very well. People who are successful with this plant are usually very successful with it. It may grow a bit more slowly than some plants but if it likes your aquarium you should have plenty to share when it gets going.

Ceratopteris

Water sprite is lovely small aquatic fern that is the only genus in it's family of Parkeriaceae. The genus is considered to have 4 or 5 species, but the only ones that are found regularly in the aquarium hobby are C. thalictroides and C. pteridoides.

Though I had kept aquarium plants previously, my first personal success with them was in the 1970's with C. pteridoides. This pretty plant was widely available at the time and grew very well for me as a floating plant in Montana in several tanks while I was in Jr. High and High school, quickly covering the tops of the tanks with it's attractive green leaves and provided cover for fry with it's long hanging roots. Small new plants formed regularly on the leaf edges of mother plants.

C. thalictroides has much more finely branched leaves than C. pteridoides and seems to be more commonly available now, and the species I currently have in my tanks. Though water sprite is generally considered an easy plant to grow, it can be a bit particular about it's water. Ceratopteris don't seem to like the hard water I get in Arizona and the only way I've been able to grow them over long periods of time here under water has been to use CO2. I have found if I'm lax in topping tanks that the water sprite will happily send leaves up above the water. In the hot dry desert they don't last a long time and it can end up looking like quite a mess as the leaves turn brown and die. I haven't had any luck in encouraging the C. thalictroides to adapt to life as a floating plant.

Water sprite can have variable appearances depending on the water it's in, whether it's floating or planted, the fertilizers, and CO2, and the lighting it's under. It's usually relatively easy to grow in most areas, but as I've mentioned if it doesn't like your water it can be a bit more challenging. I personally find the plant so attractive that it's worth the extra effort, if needed.

Marsilea

There are over 60 species of Marsilea, a small aquatic fern, that doesn't really look much like a fern at all. There is some question as to what species are being grown in the aquarium and there are probably several. I've had what is supposed to be M. quadrifolia and another mini version that is probably a different species, rather than a variety.

This is one of my favorite aquarium plants and one of the easiest ground cover plants to grow. It seems to be happy to thrive in almost any conditions. Even in the same aquarium this plant can take on very different appearing growth. It can remain small and cover the bottom of the tank, looking like a slightly larger more hardy version of Glossostigma, with single leaves, or it can go wild and grow long stems with leaves that look like 4 leaved clovers, which it gets it's common name from, or pretty much anything in between.

Generally I've found in a tank without additional CO2 and moderate lighting the plants will develop the small leaves and stay close to the ground in the front where the lighting is brightest, but as the runners spread through the aquarium and plants grow under taller light shading plants they are more likely to develop a moderately short 4-leaf form. In a totally ignored mess where the top of the tank is allowed to be covered with excess plant growth Marsilea will send tall stems up and produce large 4-leaf formed leaves above the surface of the water.

Azolla and Salvinia

Azolla and Salvinia are both genera of floating ferns that are used more often in ponds than in the aquarium. Azolla is particularly interesting because of it's symbiotic relationship with a nitrogen fixing cyanobacteria, Anabaena azollae, which makes it useful as a biological fertilizer. Azolla is also used as feed for animals.

Both Azolla and Salvinia can become invasive plants and form dense carpets covering the surface of natural waters, blocking sunlight from life beneath. If too thick they can even interfere with the exchange of oxygen and other gases at the water surface. If you grow them in the aquarium they can do the same thing, and like duckweed can become more of a problem than a benefit. I wouldn't generally recommend them as good candidates for your planted aquarium.

Ferns in your Aquarium

Aquatic ferns are beautiful aquarium plants. Most are relatively easy to grow and readily available making them perfect additions to your planted aquarium. With their variety of appearance, size and growth it would be easy to make an entire planted aquarium with just aquatic ferns. There are also many ferns and the horsetails that would be suitable for the edge of your pond or in a large vivarium. If you haven't experienced the joy of ferns in your aquarium yet, it may be time to give them a try.


Welcome to the Jungle | Into The Forest | The Creepy Crawlies | A Clearing in the Thicket | Algae Eaters for the Planted Aquarium
North American Natives | Why things go wrong Pt 1 | Why things go wrong Pt 2 (Algae) | Algae Eating Shrimp | Lo-Tech Tanks
Welcome to the Fish Room | The Stemmed Plants | Mosses | A Livebearer Biotope | Planted Tank Social | The Genus Hygrophila | Cyanobacteria
Easy Plants | What I Did Last Summer | Decorations in the Planted Tank | Botany-An Introduction to Plant Biology | Botany-Anatomy of a plant
Botany-How Plants Work | Easy Rosettes | Going High-Tech | Floating Plants | Dealing with Success | Bringing the Outside In | Vallisneria
Hair Algae | Flowering Aquarium Plants Part 1 | Flowering Aquarium Plants Part 2 | Liverworts in the Aquarium | Elements of Design
Planted Aquarium Maintenance | More Mosses | Invaders | Ferns in the Aquarium | Setting up a Planted Aquarium
Seaweeds of the Pacific Northwest | Proserpinaca | Hardware for the Planted Aquarium | Rotala | Neocaridina Shrimp | Lo-tech Tank Tips


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