Ferns ( Pteridopsida )
Order Polypodiales
Family Dryopteridaceae
Genus Bolbitis.
The green fern stem is up to one centimeter in diameter, horizontal, branching, covered on the sides, and sometimes on top, with golden-yellow rows of oblong scales and dark, more or less densely arranged hair-like scales. Leaf petioles are covered with the same scales. Leaves are bipinnate, dark green or intensely green, slightly translucent, and quite rigid.
Their sizes vary and can reach (including the petiole) a length of 60 centimeters, with a leaf blade width of 20 centimeters. Leaf petioles extend upwards from the stem in two rows, the tip of a young leaf is spirally coiled, leaf blades are positioned obliquely in the air and can assume a horizontal position in water. Roots are dense and dark brown. In a submerged position, the horizontal fern stem branches.
Vegetative reproduction—the formation of daughter plants on the fern leaves—is rare. However, young plants form on leaves separated from the main bush, much like in Microsorum, growing from the underside of the leaf. When cultivating Bolbitis, certain conditions must be met: • do not submerge the roots and stem into the substrate (at worst, press the ends of the roots with a stone, but it is better to root the plant using thread or a rubber band on a stone or driftwood); • do not move or replant the plant unnecessarily; large specimens with branching stems and more than 30 leaves are recommended to be divided. Bolbitis acclimates slowly in a new body of water, but then begins to grow and gradually reaches 40-50 centimeters. This fern is a magnificent decoration for an aquarium.
Bolbitis heudelotii. African Water Fern, Congo Fern. — Bolbitis heudelotii.
"1" (Eng. – African Bolbitis Fern, African Water Fern, Congo Fern). Native to West Africa, predominantly in waters with fast currents, sandy or rocky bottoms. The plant enjoys well-deserved popularity among aquarists and is quite widespread. However, this plant is slow-growing and quite demanding regarding maintenance conditions. For the plant to develop well, it is important to disturb it as little as possible and protect it from overgrowth. It looks very effective and can adorn any aquarium. Under favorable conditions, height reaches 30-35 cm.
The fern has a horizontal stem; in strong specimens, its diameter exceeds 1 centimeter. Stem length in nature is unlimited, while in aquariums, it rarely exceeds 25-30 centimeters. In strong plants, the stem branches. Its surface is covered with scales with yellowish edges, and a fringe of black roots extends downwards. Leaves depart upwards from the stem at equal intervals. They have a long, thin petiole, and the blade is deeply cut.
This is a typical fern with petiolate leaves and roots, as well as a rhizome densely covered with trichomes. Adult "fronds" (leaf-like organs of ferns) are dark green, deeply incised, and irregularly serrated at the edges. In shape, they somewhat resemble strongly elongated oak leaves. Leaf tissue is membranous; young leaflets unfold from bottom to top, are very attractive, deeply cut, wider at the base, and irregularly serrated at the edges. Leaves grow entirely underwater, evenly throughout the year. This plant is very dense and sinks in water, dropping to the bottom.
"2" The plant is well suited for both moderately warm and tropical aquariums. It grows best at a temperature of 23-26°C. When water temperature drops to 22°C, growth noticeably slows down. At temperatures above 28°C and insufficient nutrients, it quickly depletes. The plant does not tolerate hard water at all; for good growth, water hardness should not exceed 6°. The maximum allowable hardness is about 8°. The species prefers soft, acidic water with a pH of approximately 6.0-6.8. If Bolbitis leaves have turned black, measure the pH. Most likely, this indicator is in the alkaline range. If the pH is in the alkaline range, the leaves turn black or spotted, and in alkaline water, its leaves quickly disintegrate.
Regular water changes are desirable. It grows in any lighting conditions, feeling best under diffused light. It tolerates prolonged shading perfectly, though reacting with a decrease in growth rates. Under strong lighting, it becomes covered with algae. It is very sensitive to overgrowth by green and blue-green algae. It cannot stand cloudy water or dirt in the aquarium and achieves maximum development only in crystal-clear water. Regular water changes are also necessary. Daylight hours should be at least 12 hours.
"4" The rhizome is creeping, fibrous, scaly, up to 1 cm thick, dark green, sometimes brown, branching, with poorly developed adventitious roots. No substrate is required for the plant’s development. Bolbitis can be grown without substrate. It feels best when attached to driftwood and rocks. Its roots—rhizoids—easily grow into the slightest irregularities of the stones placed under it, enveloping them like a net.
Its stem and roots require a strong oxygen supply, so burying them in the substrate is strictly prohibited; the stem must be above the substrate and well-lit. If buried, the plant stretches out, its leaves turn brown, and it soon dies. Mineral supplementation is essential at high water temperatures and a lack of organic matter at the bottom. Mineral fertilizers should be applied regularly in small doses and must contain trace elements.
"5" Planting Bolbitis causes no trouble. This plant is heavier than water, so if thrown into the aquarium, its roots naturally settle on the substrate. Having settled on a stone or driftwood, the fern soon firmly attaches to them, but if necessary, the bush can be easily detached from the substrate. However, do not cover the roots with substrate—this depresses the plant and can lead to its death. It can be grown in an aquarium of any capacity, placing it usually in the corners, in dimly lit places, on large stones or rock piles. During planting, branches can be trimmed completely; within a few weeks, it will grow with renewed energy and better adapt to underwater life.
It dislikes being close to other plants, which is why it is planted in an open area of the bottom. Dense foliage is not only highly decorative but also serves as an excellent refuge for juveniles. Although it can develop well in an aquarium without strong water circulation, it undoubtedly grows better in moving water (for example, near filters). In 2.5-3 months, the bush doubles its mass. Several leaves develop in parallel on the rhizome, and the process of uncoiling the leaf spiral takes no more than one to two weeks. Planting density is 1 plant per 20 cm2.
If there is a water current in the aquarium, regardless of the initial direction of leaf growth, eventually they all lie in one direction—along the current, making the bush look very original. It looks especially decorative on driftwood or a large stone with a rough surface. The creeping rhizome firmly attaches to the surface and quickly covers it with dark green, very attractive leaves. To grow Bolbitis on the bottom, plastic suction cups can be used so that its roots only touch the bottom or lie on it.
It grows quite well if there are adult, strong plants and we create good conditions for it, i.e., clean water that is moderately warm and soft. For the plant to develop well, it is important to disturb it as little as possible and protect it from overgrowth. It is advisable to periodically reduce the bush size by cutting rhizomes into parts, as rhizomes creep across the bottom and intertwine. Aquarists should remember that Bolbitis strongly dislikes an excess of sodium in the water. Therefore, adding table salt and baking soda to the aquarium should only be done out of great necessity and in very small doses.
"6" The rhizome has a large number of growth points, and practically from any, even a not very large section of the rhizome with a few already developed leaves, a new plant can be obtained. It propagates by dividing the rhizome, which should be cut with a sharp razor into several parts so that each has at least three strong leaves and a growth point. A new plant forms from each separated rhizome section with several leaves.
The separated parts should be pressed to the bottom using a small stone, under no circumstances burying the rhizome in the substrate. Daughter plants form very rarely, even in strong specimens. The appearance of plantlets can be stimulated by cutting off a fully unfolded young leaf and fixing it on a well-lit area of the substrate upside down.
Identification: Bolbitis heudelotii.
Bolbitis heteroclita.
Distributed in the tropics of Southeast Asia. Height 30-40 cm. The plant is very decorative. Young plants of this species bear a strong resemblance to Ceratopteris. The rhizome is creeping, greenish-brown, up to 1 cm thick, with dark brown to black adventitious roots, densely covered with brown scales.
Leaves can range in shape from oval or lanceolate with a pointed apex to trilobed, and have strongly pronounced corrugation. Leaf petioles are located on the rhizome in two or three rows with varying distances. The leaf blade is simple or odd-pinnate, in small specimens often three-lobed with a petiolate terminal leaflet. Submerged leaves are light green to green with a pleasant coloration, usually with a pair of lateral leaflets at the base.
Daughter plants may form on the leaves of the parent plant. Vegetative reproduction is also possible by dividing the rhizome into separate parts, each of which must have at least 3-4 leaves. Spore capsules sometimes form on the underside of certain leaves. It grows very slowly. Sensitive to transplantation. Since the rhizome does not root in the substrate, it must be secured to decorative items such as stones or driftwood. Soft, acidic water, moderate lighting, and a temperature not exceeding 25°C are recommended.
A species poorly suited for aquarium cultivation. It tolerates submersion for about half a year, but its growth practically stops during this time. Even if it forms 3-4 leaves, each subsequent one is smaller than the previous. Afterwards, sudden death of the plant may occur. The fern can be wonderfully used in a paludarium, where it grows well in moist soil.
Marsilea quadrifolia, Marsilea crenata, Marsilea hirsute, Pilularia globulifera.
Azolla caroliniana, Azolla filiculoides, Azolla pinnata, Azolla. 
