Ferns ( Pteridopsida )
Order Salviniales ( Salviniales )
Family Salviniaceae ( Salviniaceae )
Genus Salvinia — Salvinia.
Salvinia species grow on the surface of standing and slow-flowing waters, sometimes forming dense thickets that block light access to the water body. Salvinia is a plant with a thin horizontal stem 10-15 centimeters long. The stem bears whorls of three leaves each. Two of these leaves are broad, lamellar, and floating, located on the water surface. The third leaf is unusual: it extends downwards from the stem and resembles a bundle of roots in appearance. The plant has no true roots.
The floating leaves are oval, entire-margined, and contain air cavities (aerochambers). The surface of the floating leaves is covered with special stellate hairs that ensure they are non-wettable. If the floating leaves are submerged in water, the hairs trap air bubbles near the leaf surface, making the leaves sparkle like silver. If a wave or fish movement turns Salvinia upside down on the water surface, the air bubbles allow it to quickly return to its normal position.
Like most aquatic plants, Salvinia multiplies rapidly during the growing season. Tiny stem fragments are carried away by currents and water inhabitants, forming new thickets. Tropical species of Salvinia are often kept in aquariums, but the plants never reach the sizes they do in nature. Salvinia requires soft water (up to 10° hardness) with a temperature of 20 to 30°C and strong lighting.
It should be noted that in dry indoor air, the floating leaves of the fern turn yellow, dry out, and deteriorate. Conversely, in an aquarium tightly covered with a lid, the air is excessively humid, and the leaf hairs, once wet, lose their ability to trap bubbles. The leaves gradually become waterlogged and die. The optimal option is to cover the aquarium with a lid, but open it twice a day for ventilation.
Water spangles — Salvinia natans.
“1” Distributed in water bodies of Europe, North Africa, and Asia Minor. Salvinia belongs to ferns, has very thin branched stems with brightly green leaflets extending symmetrically from them, covered with fine hairs that make them water-resistant. The plant has short stems bearing pubescent oval leaves up to 1.5 cm long, in whorls of three. Moreover, from each whorl, two leaves are on the water surface, while the third is seemingly dissected into threads and looks like numerous hairy rootlets. Actually, the plant has no roots; their role is performed by underwater leaves that absorb nutrients dissolved in the water. The leaves floating on the water surface are responsible for photosynthesis. The plant develops well in summer, but usually dies in winter. Under very favorable conditions, it can be grown year-round.
“2” Salvinia can be kept in moderately warm and tropical aquariums. It grows satisfactorily at a temperature of 20-28°C, but reaches maximum size only in a warm aquarium at temperatures above 24°C. In cold water, Salvinia grows very slowly, and its leaves become small. The plant develops well in both very soft and fairly hard water. Regular water changes are desirable. Lighting must be very bright (0.7 W/L). It grows best in sunlight and high air humidity.
“4” Pale leaves signal a lack of micronutrients.
“5” Salvinia forms a beautiful green carpet on the water surface, which serves as a natural light filter and provides excellent shelter for fry and other small fish. It dislikes dry air; a cover glass is mandatory to maintain high air humidity. It is used to shade other plants. It helps prevent algae outbreaks by shading parts of the aquarium and clearing the water of nitrates. In nature, Salvinia is a seasonal annual plant that dies in winter and sprouts from spores in spring. Under favorable aquarium conditions, the plant will delight the eye all year round.
“6” Salvinia natans reproduces by both spores and stem shoots. In aquarium conditions, the only method of propagation is vegetative. A piece of the stem with leaves is chosen from the mother bush and detached — the separated bush, under good maintenance conditions, will soon turn into a large plant.
Identification: Salvinia natans — Salvinia natans.
Eared watermoss — Salvinia auriculata.
“1” Distributed in standing and slow-flowing waters of tropical America. A floating plant. The size of the plant depends on growing conditions and ranges from 3 to 6 cm. The stem is thin and fragile. A floating plant with two types of leaves: floating on the water surface (aerial) and underwater, resembling roots, with a dissected blade and long hairs.
Round, somewhat convex pale green aerial leaves are located on short petioles pairwise opposite each other on the stem. The upper side of the leaves is covered with hairs; the underside is green with a brownish tint. Thin, delicate, modified underwater leaves extend from each pair of aerial leaves. Salvinia is stably held on the water surface due to the special arrangement of the plant’s organs. The leaf blade touches the water only by its edge and midrib; on both sides of the leaf, there are two bulges like two sacs, with an air bubble in each. The lobe of the plant’s leaf is ear-shaped, which is why Salvinia received this name.
“2” The plant grows and reproduces well in the aquarium under top lighting, with water and air temperatures of 25°C in summer and 20°C in winter. The plant is demanding regarding lighting — it dies with insufficient light and low temperature. The culture is easily restored from surviving spores of dead plants. To do this, the temperature should be raised to 25-30°C and bright, diffused lighting established. In winter, it is well preserved with supplementary lighting lasting 12-14 hours a day.
“5” One of the most useful and decorative aquarium plants. A floating fern that prevents light penetration to deep layers and, just like duckweed, absorbs excess nutrients. However, unlike duckweeds, due to its impressive size, it can be removed from the aquarium without much effort. It serves as a reliable refuge for livebearer fry and can be used for natural shading.
“6” It propagates vegetatively by division of the stem creeping along the water and by spores.
Aquarium water mosses, Bryophyta, Marchantiophyta.
Ceratopteris cornuta, Ceratopteris pteridoides, Water sprite. 
