Ferns ( Pteridopsida )
Order Polypodiales
Family Pteridaceae
Genus Ceratopteris.
Horned fern — Ceratopteris cornuta.
“1” Synonym: Ceratopteris siliquosa. It is distributed in Southeast Asia, Northern Australia, East Africa, from central South America to southeastern North America. The plant got its name due to the similarity of leaf lobes with horns. This species is best suited for rooting in substrate in aquarium conditions and is considered the most beautiful of all four species. The shape of the light green leaves of the fern changes during its life: initially the leaves are whole, then they become notched and lobed, and at middle age they have a pinnately dissected shape. This is one of the species that does equally well both as a rooting plant and as a floating plant. Light green figured leaves are located in the form of a rosette. It has beautiful finely dissected light green leaves, the edge of the leaf bends downwards, which in the aquarium under favorable conditions reach a height of 40-50 cm. Bush width is 10-20 cm. The leaves are very brittle and require careful handling.
“2” Maintenance conditions for Ceratopteris with various leaf shapes are the same. The plant is best suited for keeping in a tropical aquarium at a temperature of 22-26°C. At temperatures below 20°C, its growth slows down significantly, and the leaves become small. The water fern develops somewhat better in soft water. The water must be soft – hardness no more than 7°, with a neutral or slightly acidic reaction. The plant feels better in old, slightly acidic water. In hard water with an alkaline reaction, the plant degrades. Constant water changes are not necessary; the fern grows well in old water with a high content of humic acids.
Lighting is strong (0.5 W/l). This is one of the light-loving plants, so it must be placed closer to the light source. In bright lighting, it should be used as a natural light filter protecting other plants from algae overgrowth. With good lighting, it grows very quickly, preventing the formation of algae, as it absorbs a large amount of nutrients from the water. Daylight hours should be at least 12 hours.
“4” The root system of the plant is quite well developed, but its roots are tender and brittle. Therefore, the substrate should consist of small particles and be well silted. Coarse sand is best suited as a substrate. There can be a lot of silt at the bottom. In this case, the fern is not afraid of an excess of calcium-containing rocks. The substrate can be laid in a layer up to 4-5 cm thick. This fern does not need special mineral fertilization; on the contrary, it is very sensitive to an excess of mineral substances. The nutrition obtained from the soil and water is quite sufficient for the plant.
“5” It can be planted in the soil of a deep aquarium and grown floating on the water surface. It can also grow as a floating plant, the roots of floating plants provide good protection for fry and young fish. Planted in the background and along the side walls. In small open aquariums, it can grow outward and form very beautiful, carved leaves on the water surface, which are highly decorative and contrast with other plants. In bright light, it grows very quickly and fights algae growth by consuming a large amount of nutrients. Excellent for starting small aquariums.
“6” The fern propagates easily and originally, by forming daughter plants on the old leaves of the mother bush, especially at breakage sites. After the formation of several small leaves and a root tuft, the daughter plant breaks off and floats to the water surface, and very soon the entire aquarium is covered with floating Ceratopteris. Floating offshoots have a root system, so they are easy to plant in the aquarium soil. The mother plant begins to die off and needs to be replaced.
Cabbage fern, “Water cabbage” — Ceratopteris pteridoides.
“1” The homeland of the plant ranges from the Amazon to Peru and from Panama to Guatemala. Single populations are also found in northern Argentina, Brazil, Paraguay, and it is widely distributed in tropical regions of the globe. It inhabits water bodies with standing or sluggish water, floating on the water surface or rooting in moist soil. It forms a compact rosette of thin, translucent, light-green leaves creeping along the water, resembling an opened head of cabbage in shape, which is why this fern got its common name water cabbage. In size, the plant can reach over 30 cm.
Leaves of various shapes, light green with wide, slightly incised edges, lying on the water surface or rising above it. The leaf blade is usually triangular in contours, from almost undivided to three-lobed in the shape of a palm, eventually changing from incised to pinnately divided. The leaf blade of the water cabbage is wide with deep cuts along the edges, reaching quite large sizes. The veins and petioles of the plant are very fragile, spongy in property. Beautifully shaped leaves are arranged in a rosette. Brown roots gathered in a bunch extend downwards from its middle. Under favorable conditions, the fern leaves reach 10-15 cm in length. The leaves of this fern are somewhat denser and darker in color than those of the other two.
“2” It feels great in sluggish water with a hardness of up to 15°, neutral reaction, at a temperature of 25°, but also tolerates lower temperatures. In hard, slightly alkaline water, it quickly loses color saturation and disintegrates. When deviating from favorable conditions, it loses color saturation and gradually disintegrates. Water cabbage grows well under bright, prolonged lighting.
“4” Rhizome up to 3 cm long, 2 mm thick. The roots of the fern are tangled, heavily branched. Normal growth and development require water with an abundance of dissolved organics.
“5” In contrast to Ceratopteris cornuta and Ceraptopteris thalictroides, which have established themselves as excellent aquarium plants, Ceratopteris pteridoides is very difficult to care for and therefore very rarely cultivated. It is best kept as a floating plant over silted soil, under intense lighting, in sluggish water. Hair-like, lush roots in a large aquarium are a wonderful refuge for fry, where they can also easily find food and a spawning site for many aquarium fish. Moist, warm air is necessary, but a high content of water vapor causes drops to stop rolling off the leaf surface, and they rot. The plant tolerates condensation on the leaves poorly, so the aquarium for keeping this plant should be semi-covered.
A planted bush looks more effective in the background or along the perimeter of the aquarium. If the plant is left floating, it forms a rosette of graceful light green translucent leaves spread across the water. This aquarium plant is a wonderful natural filter, actively participating in the metabolic processes of the aquarium, perfectly assimilating the waste products of the aquarium inhabitants. In addition, the plant acts as a good light diffuser, creating a comfortable environment in the aquarium. Does not like frequent disturbance. Does not like intense current and frequent disturbance. The leaves are very brittle and require careful handling.
“6” Water cabbage propagates by daughter plants that appear anywhere on the leaf blade, resembling bows. Many of them appear especially at breakage sites.
Salvinia natans, Salvinia auriculata, Salvinia.
Ceratopteris thalictroides, Indian fern (Ceratopteris). 
