Classification of aquatic plants by groups.
Continued…
Light consumption in the red part of the spectrum by plants is 100%, in the yellow – 60%, and in the blue – about 40%. Their physiological radiation ranges from 300 to 800 nm, i.e., in addition to the visible part of the spectrum, insignificant ultraviolet and infrared ranges are also captured. Illumination in the tropics ranges from 20 to 60 thousand lx. It is desirable to reproduce its lower limit in the aquarium.
Depending on the duration of daylight, plants are divided into: • Short-day plants growing in the tropics and subtropics. They flower only if the daylight duration is less than 12 hours; • Long-day plants growing in temperate latitudes. They flower when daylight is more than 12 hours; • Plants neutral to lighting duration, whose flowering does not depend on this factor. Leaves floating in the water column receive less solar energy because the amount of light decreases as it passes through the water column. Light-loving plants need more light than shade-tolerant ones.
Plants such as *Anubias* and ferns are easier to grow because they are shade-tolerant. They have adapted very well to the lack of light in their environment and are therefore adaptable plants. Plants with needle-shaped leaves that grow in a circle are difficult to grow because they require a lot of light and a lot of CO2. They do not adapt like shade-tolerant plants, but they do not differ from other plants in any other preference. When setting up an aquarium, light-loving plants should be planted directly under the lamp and a place should be reserved for shade-tolerant plants away from the lamp.
Plants can grow in closed, semi-closed, and open soil. According to the shape of the plants and the specifics of their placement in the aquarium, aquarium plants can be divided into several groups:
Plants rooting in the substrate. The group of plants rooting in the substrate includes plants with a well-developed root system. Aquatic plants rooting in the substrate absorb nutrients both from the surrounding water over their entire leaf surface and through hydropods, and with the help of roots from the so-called soil solution. They have a dense rhizome and well-developed leaves. These plants require a soil layer of 5-10 cm. The composition of the soil in the aquarium is important for them.
Some plant species are content with poor soil, while others definitely need fertilizer supplementation. If spots, holes, and other defects begin to form on the leaves, it means the plant needs feeding. They reproduce vegetatively, as well as by seeds and rhizome division. This includes well-known aquarium plants such as *Vallisneria*, *Sagittaria*, *Nuphar*, *Tradescantia*, and others.
Plants attached to the bottom of the reservoir: • flowering under water and completely unassociated with the air environment, for example, *Najas*; • completely submerged in water and bringing only flowers and inflorescences to the surface, for example, water buttercups (*Ranunculus*), *Vallisneria*, *Myriophyllum*, etc.
Plants rooting in the substrate receive the main part of mineral salts through the root system directly from the soil, and carbon dioxide from the water or air. Their root system is strongly developed. Roots grow from the stem, which merges with the rhizome. Leaves form on the upper part of the stem. Along with the formation of leaves, embryos are laid in the stem, from which new roots, shoots, or flower stalks subsequently form under the action of certain hormones.
Stems can be located vertically, horizontally, below or above the soil level. In some *Anubias* species, even in an aquarium, the rhizome can reach several tens of centimeters in length. The leaves of these plants often have pronounced petioles. Leaf blade dissection is weak. Some plants are shade-tolerant (but not shade-loving, although in nature they are shaded by various objects). Plants from this group actively absorb nutrients in the soil, and only in some cases large specimens require feeding. A large amount of organic matter in the soil should be avoided, as this can lead to root rot. *Cryptocoryne*, *Echinodorus*, *Aponogeton*, and *Anubias* are the most widespread.
Plants rooting at the bottom of the reservoir and forming leaves floating on the water surface and flowering above water. Plants in this group usually develop two categories of leaves – submerged and floating. Submerged leaves are usually simple, thin, delicate, and pale in color, sometimes whorled, dissected into narrow lobes. Floating leaves are simple, thick-walled, brighter in color, often shiny on top, covered with a non-wetting composition. Most plants in this group develop creeping or tuberous rhizomes. Plants reproduce by seeds and vegetatively, and some species only by seeds. These plants need nutritious soil, especially during the flowering period.
Plants living at the bottom of the reservoir or near the water surface. These are the most primitive plants among higher plants. For the life of plants in this group, water contains all the necessary substances, and only light comes from the external environment. Among higher plants, bryophytes have the most primitive structure, especially liverworts. The body of leafy mosses is usually divided into stems and leaves; roots are absent. Attachment to the substrate is carried out by rhizoids. Bryophytes reproduce vegetatively, asexually (spores), and, exceptionally rarely, sexually.
The amount of oxygen entering the water is determined by the total surface area of aquatic plants. The larger it is, the more oxygen the plants release. It should be noted that a larger surface area is characteristic not of broad-leaved plants, but rather of plants with many thin feathery leaves – such as *Cabomba*, *Myriophyllum*, *Egeria*, Java moss (*Vesicularia dubyana*), and Indian water fern. Perhaps the most unpretentious plant for a new aquarium is Java moss (*Vesicularia dubyana*). This plant, resembling tangled dark green threads, is extremely shade-tolerant and unpretentious. It does not need to be planted in the substrate because it has no roots. It can grow on decor elements, attaching to them independently, in a humid environment above the water level and under water, which creates a wonderful natural effect.
Plants freely floating in the water column or near its surface receive all nutrients from it, usually unattached to the substrate. They absorb nutrients over their entire body surface and can thus use only substances dissolved in water. Plants in this group have a poorly developed root system, and sometimes it is completely absent. Their roots are usually fibrous or creeping, serving to anchor the plant. Leaves are usually whorled, dissected, stems are branched or slightly branched, and in Lemnaceae the stem is transformed into a flat or slightly convex plate. They have finely dissected leaves that serve to absorb organic and inorganic compounds dissolved in water.
These plants actively oxygenate water, serve as spawning grounds and shelters for fry, and even as a food supplement for some fish species. They need water filtration because they are sensitive to leaf contamination and temperature changes. They are convenient to use in a new aquarium when other plants are lacking. For the winter, free-floating plants usually sink to the deep layers of water or to the very bottom of the reservoir, and many of them (*Utricularia*, *Ceratophyllum*) form special overwintering buds. They usually reproduce vegetatively. This group includes *Riccia*, *Najas*, *Utricularia*, and *Lagarosiphon*.
Bog and coastal plants attached to the bottom of the reservoir and significantly rising above the water. Plants in this group develop well outside of water, in highly moistened places, especially in wet meadows, lowland bogs, and swampy forests. This group of plants is intermediate between terrestrial and aquatic plants. Some plants migrated into the water during evolution, while their ancestors lived on land for a long time. Such hydrophytes are considered secondary aquatic.
Plants floating on the water surface have special body structure features. The leaves of this group are delicate, with a large surface area. Air cavities and storage chambers are well developed in the leaves or leaf-like stems and petioles. In this group of plants, leaves have a bristly or smooth surface covered with a non-wetting composition (water rolls off freely from such a surface). Plant roots are fibrous, heavily overgrown, thin, usually ciliate; absent in some plant species. Such an organ structure helps plants stay on the water surface. Plants floating on the water surface absorb nutrients mainly through their roots, keeping their leaves hydrophobic to absorb carbon dioxide from atmospheric air, where it is more accessible (compared to the aquatic environment). Sometimes their life can proceed both in the water column and on the surface. For example, *Lemna trisulca* rises to the water surface only during flowering.
Plants floating on the water surface perform several important tasks: they protect the aquarium from excessively bright sunlight, serve as a spawning ground for many fish, and contribute to biological balance in an artificial reservoir. These decorative plants can assimilate fish waste products, can serve for building nests, and can be a shelter for fry. They receive nutrition directly from the water through roots or the lower parts of leaf blades. Carbon dioxide is absorbed from the air. Oxygen is released directly into the atmosphere. All plants in this group need bright lighting, grow quickly, and reproduce. Strong development of floating plants worsens the illumination of the water column and significantly weakens gas exchange in the substrate, which often leads to its rotting. This group includes *Salvinia*, *Pistia*, *Lemna*, and others.
Floating plants are an excellent means of decorating a home aquarium, and functionally they are very useful: they actively consume substances dissolved in water, serve as natural light diffusers, are used by fish as a substrate for spawning, and provide fry with a comfortable and safe refuge. The species composition of hydrophytes of this group suitable for amateur aquaculture is relatively small, but at the same time quite diverse. However, the absolute majority of home aquariums are closed vessels observed not from above, but from the side. That is, we have to contemplate not so much the face of the green carpet as its underside. So let’s try to evaluate the floating flora from this perspective.
*Riccia* deserves the maximum rating. For this liverwort, the concepts of obverse and reverse simply do not exist. The carpet is identical (and beautiful) on both sides. At the other pole is the water hyacinth (*Eichornia crassipes*): as pleasant as this floating masterpiece is from the outside, it is just as sloppy when viewed from the inside – from the underwater side. The root system of *Eichornia crassipes* is mighty, fluffy, but its color ranges from yellowish-brown to black, unattractive and rather untidy.
The situation is slightly better with some Salvinias, in particular *Salvinia auriculata*, whose roots, although more compact (compared to *Eichornia*), also have a pronounced brown tint and outwardly resemble fragments of decomposing vegetation. True, in *Salvinia cucullata*, the underwater part looks much neater, which makes it possible not to write off the use of representatives of the genus in forming a carpet on the water surface.
In *Pistia stratiotes*, the roots are also dark, but they are somehow better organized in space, do not cause rejection, and do not give the aquarium a neglected tint. *Limnobium* plants are very good. Although the roots of *Limnobium laevigatum* are long, they are light, delicate, and quite neat. The underside of the floating carpet formed by them, even if it is not a true decoration of the decorative container, is nevertheless not devoid of some decorativeness. Many perceive duckweed as a weed plant. However, in my opinion, in terms of decorativeness, it is little inferior to *Riccia*. The thin, short, whitish-green rootlets of *Lemna minor* form a very picturesque pile, softly outlining the water-air boundary and giving a certain completeness to the aquarium composition as a whole.
Aquarium plants, – what are they?
Aquatic plants, unlike terrestrial ones, can absorb water not only through roots, but also through their entire surface. They are divided into three types:
• plants that assimilate water through the root system (*Cryptocoryne*). They need soil containing nutrients.
• plants that assimilate water through both roots and leaves (*Echinodorus*). They need soil with a low nutrient content.
• aquatic and floating plants that assimilate water mainly or exclusively through leaves (*Elodea*).
Depending on the structure and characteristics of the leaves, submerged and bog plants can be divided into seven groups:
1. Plants with ribbon-like or thread-like leaves. Good oxygen producers. Prefer a bright place. Among them, there are species that form a turf cover. Attach the offshoots to the substrate with a glass pin or stones. Since most of these plants also require nutrition through roots, pot culture is needed. Rhizomes can be divided.
2. With coarse or moss-like leaves. Good oxygen producers. Serve for spawning and form excellent shelters. Since these plants assimilate the substances they need only through pores, they can be attached to the substrate with a glass pin or flat stones until they grow root-like rhizoids. Reproduce by shoots or cuttings. A bright place is recommended.
3. With petiolate leaves. These plants prefer subdued light and soft water. Depending on the species, pot culture may be recommended. *Cryptocoryne* should not be placed together with *Vallisneria* and *Sagittaria*!
4. With finely feathery leaves. The most active oxygen producers; some of them (*Cabomba*) require very soft water, almost always require a lot of light, and do not tolerate flowering and dirty water. Serve for spawning and as shelters. Since they need roots only as an anchor, they should be planted in groups and attached to the substrate. Reproduce by cuttings.
5. Floating on the surface and in the water column. Serve for spawning. Require a lot of light. Floating plants can cover only 1/3 of the total aquarium surface. Need constant aeration and are most often sensitive to condensation moisture. There should be no top glass.
6. With floating leaves. It is advisable to plant these plants in pots or shallow bowls. Require strong top lighting.
7. Bog plants. Well suited for aquariums where the bottom is laid out in terraces: this gives them the opportunity to grow above the water surface.
Plant types: 1. – Plants with ribbon-like or thread-like; 2. – With coarse or moss-like; 3. – With petiolate; 4. – With finely feathery leaves; 5. – Floating on the surface and in the water column; 6. – Plants with floating leaves; 7. – Bog plants.
Geographical origin of aquarium plants.
Classification of aquatic plants by groups. Hydrophytes. 
