Java Fern (Microsorum pteropus). This amphibious fern is widely distributed through southeast Asia, northwards to southern China, and throughout Indonesia to the Philippines. It's said to thrive even out of water, as long as it's in a spray zone and constantly wet. Nevertheless, I find that even in the humid air under a glass top Microsorum's emerse leaf tips blacken. Quite tolerant of moderate light, Java Fern can also adapt to hard water and even to some salt. It's the Rift Lake cichlid keeper's mainstay.

Java Fern is very plastic. Some forms of it seem pretty stable, like the two sports discovered in one of their greenhouses in 1991 and distributed by the Danish firm Tropica, one named "Windeløv" for their founder and the other named "Tropica." The Dept. of Agriculture protects our Florida aquatic plantfarmers by forbidding imports, but a mutation very like "Tropica" is in the American trade, offered as "Java Lace Fern."

Genetic mutations aren't the only causes of changes. At other times, shifting parameters of pH, carbonate hardness, availability of nutrients and light intensity combine to reshape the form of Java Fern. Two main types that are morphologically quite consistent across a range of growing conditions are distinguished: a robust form and a gracile form.

The robust form is larger in every part, with broad undivided fronds up to a foot long, often with a lobed or trilobed base, of a bright mid-green, very puckered and quilted between the side veins, with ruffled edges. This familiar robust form has fronds spaced more widely along the scaly running rhizome. Its spores are scattered over the undersides. Soren Reinke's good close-up pix will show you what these various parts of Java Fern look like, if you have any identification doubts.

The other, gracile form is much smaller, with narrower (less than ¾ inch across), lanceolate darker green leaves that aren't so ruffled, which form a denser, more clumped growth. Its spore cases are neatly arranged in rows flanking the midrib. Tropica distributes a form like this one as Microsorum species "narrow." Some plant pros, like Dave Gomberg, suggest that this smaller variant is actually Microsorum blassii, found in New Guinea and nearby islands at the edges of small lowland streams, often growing completely submerse. Christel Kasselmann, in Aquarium Plants, 2003, treats the two forms as a single species.

It is "MY-kro-SOR-um," by the way, not spelled or pronounced "MY-kro-SOR-ee-um." Microsorum means "tiny spore," a name that would apply to pretty much any fern, I'd think; pteropus ("terr-OH-pus") refers to the "winged base" of vigorously growing leaves on a well-established rhizome of the robust form. Sometimes you may find minute plants growing from the sporecases, especially as an over-mature leaf slowly distintegrates. But Java Fern reproduces itself more vigorously from the plantlets that develop along the outward edges of mature leaves. In time they can be gently separated, rootlets and all. And it also reproduces in the more conventional way, with offsets from the running rhizome, which is the main green root along which the leaves sprout.

When the plantlets sprouting from overmature leaftips have three or four well-developed leaves and some trailing roots, I separate them. I fold a plant weight-strip in half like a bobby pin and thread the plantlets onto one leg. I crimp it lightly and set the group down where it will get plenty of light but I can't see it: a watched pot never boils. Undisturbed and weighted, the young Java Ferns develop in a nice orderly way, fronds all rising from the rhizome in the same direction, hopefully. Months later I'll separate the juveniles and attach them, two and three at a time, to coconut shells or pumice rock.

The one trick to success with Java Fern, everyone agrees, is not to bury that rhizome. When I've inadvertently buried a rhizome of the gracile form in fine gravel, the leaves that continued to sprout from it became further dwarfed to a couple of inches long. Not absolutely invariably such a very bad idea: they have worked well like this for several years in a 10-gallon tank. From the rhizome also spring the copious brown thready roots, which act more as holdfasts for the plant than as conduits for nutrients. Don't hesitate to shorten them with scissors to a convenient length when you are dividing and resetting your Java Fern.

I was taught not long ago to staple the roots (not the green rhizome) to coconut shell: this gives me a portable Java Fern and a portable coconut shell cave: endless possibilities, eh? And I can lift out the whole unit to cut away any tired-looking leaves. Or to net a wily fish.

In very soft water, where pH has a tendency to drop, Java Fern can undergo a kind of meltdown when pH hits 6.0. In this meltdown, the leaves go translucent, starting at their tips; I've seen it characterized as a disease, but I think it's just a reaction to pH stress. Plant nibblers avoid Java Fern, and the compilers of Baensch, Aquarium Atlas vol. I, reported that some Scats that ate it died. This tale has certainly lost no momentum since: I see it retold endlessly. Even if it isn't acutely toxic, doubtless there are phenols and suchlike in Java Fern's leaves that make it an undesirable fish salad.

Bolbitis Fern (Bolbitis heudelotti). This is an African fern that runs along a rhizome the way Java Fern does, and similarly it doesn't want its rhizome buried. Bolbitis also works well grown on coconut shell. It's another plant with modest light requirements, but in low light its growth will be agonizingly slow. Put your Bolbitis where strong current flows; in stagnant water it seems to stifle. I'm told that Bolbitis is not an easy plant where pH levels are >7.0.

Bolbitis' dark green contrasts nicely with the clearer, lighter green of Java fern, and its conventionally fernlike divided fronds contrast well with plants that have big unbroken leaf blades. The dark blue-green of Bolbitis fern in the background gives an impression of depth to plantings in our somewhat too shallow standard tanks.

There are other species of Bolbitis sold as aquarium plants from time to time, but B. heudelotti is the easy one to grow. Back in Nov 1998, Karen Randall had a good brief piece about Bolbitis species in her "Aquatic Horticulture" article in Aquarium Frontiers. In it she noted,

"There appear to be two plants that are both being sold under the name B. heudelotti at this time. One has a shorter petiole, curlier leaves and tolerates soft water quite well. The other has petioles almost as long as the leaf itself. The leaves are flatter, with less curl to the edges and the plant does better in water of moderate hardness. In my tanks, the smaller variety grows to approximately 12 inches, while the larger easily reaches 18 to 20 inches in height. There is some speculation that while the larger plant is clearly a Bolbitis, it might actually be a different species."

Water Sprite (Ceratopteris cornuta). This variable fern is the major floating plant for most indoor aquaria. My own water is soft, but highly-buffered, alkaline water wouldn't faze it.

I always think of Water Sprite as a rosette-forming plant, but if I look closely at a mature floating clump, I'm reminded that the rhizome stands vertically, and round it the fronds arise, so closely spaced that a rosette-like form results. As a young plant develops, its leaves develop deep sinuses, like an oak leaf. In damp air they can build into large mounds. It may be worthwhile for you to drop the water level to enjoy the display. As the clump matures, submerged leaves become more deeply divided and carry fewer adventitious plantlets along their margins. Finally, it may pay to trim the roots a little and plant the mature Water Sprite. Then, with its deeply dissected pinnate leaves, similar to Meadow-Rue (Thalictrum) of gardens, you may want to call it Ceratopteris thalictroides. The question whether these are two species of Ceratopteris or one variable one, divides botanists. Christel Kasselmann, in Aquarium Plants, 2003, treats them as two species, and she has a great deal more experience than I have.

In the floating form, the roots hang down in tufts, each root in a haze of all-but-invisible rootlets : a complex microhabitat with a rich biofilm that supports fry and from which pencilfish selectively pick. Because it has aerial leaves, floating Water Sprite draws CO₂ directly from the atmosphere. This helps it thrive in hard water, where most of the available carbon has translated from carbon dioxide to carbonates. If you were to permit the older leaves of Water Sprite to yellow and decay in the water, they would be re-releasing the nitrogen locked up in their structure. Don't let that happen. Once every few months, I remove overgrown rosettes and pluck the best young plants off the edges of the mature leaves, where they have formed. I return the fresh young offsets to the tank and discard the leggy old rosette. Maybe I should give it more light, plant it, and call it C. thalictroides.

Quillworts (Lycopsidae).

Isoëtes flaccida (Soft Quillwort). Quillwort grows in a clump of very slender quill-like leaves that are square in section; if you roll one gently between your fingers you'll feel its corners. The leaves have a sporecase embedded at their base that reminds me a little of chives. Quillwort isn't related to chives at all; in fact it's an unusual survivor of a just-about-extinct class of plants, the Lycopsids, which evolved even before the ferns. The handful of other surviving Lycopsids include club mosses, but the real Lycopsid heyday was in the Paleozoic, say 300 million years ago. Then giant tufty-headed Lycopsid "trees" fell over in stagnant swamps and started turning to peat --and eventually to coal.

American aquarists get to use Quillwort more than Europeans, because the European species tend to flag when exposed to the warm waters of tropical aquaria, and they're even more brittle than the American Isoetes, almost too brittle to use. The Isoetes species from the American southeast is named "flaccida " precisely because it will bend without breaking. Quillwort is a little demanding about light levels, and it is better when temperatures don't get much over 75°F. Quillwort will stand out of low-growing gravel-covering plants like a tuft of grass. It's useful for this, since no other plant is quite like it. Perhaps I grow it partly for its strangeness.