Subclass Caryophyllidae
Order Caryophyllales
Family Amaranthaceae
Genus Alternanthera
Only a few species originating from the tropics of South America and their garden varieties can grow and develop in a submerged state. Other species can be grown just like regular heat-loving greenhouse plants. As a rule, after a couple of months, Alternanthera dies because sellers never mention that Alternanthera is a fussy bog plant. In Moscow tap water, Alternanthera grows wonderfully only when supplemented with pressurized CO2. In addition, ferrous iron supplementation is required. It is mandatory to replace 25% of the water weekly. Alternanthera noticeably accelerates growth after a water change. The optimal temperature is 18–25 °C. The content of phosphates and nitrates in the water should be minimal; otherwise, the leaves become overgrown with green algae. It grows very poorly in clean gravel.
For planting in an aquarium, large cuttings with a length of at least 20 cm should be used. Small cuttings do not grow well. Its biggest drawback is the tendency to get overgrown with algae. Under good conditions, it grows too fast. Moreover, when the top of the plant is 5 cm away from the water surface, it sharply increases its growth rate and literally reaches the air in 2 days. If the top has been in the air for at least a day, such a cutting will subsequently grow poorly in water. That is, one must ensure that the top does not emerge into the air and cut the plant into a cutting in advance.
This is an attractive but difficult-to-maintain plant. It includes various cultivars expressed in the color palette of the leaves — pink, purple, and red. The upper side of the leaves is olive-green, pale green, or reddish underneath. Planting these plants in a row creates beautiful contrasting compositions. In the aquarium, it contrasts with plants of various shades of green. It can be stated with confidence that the brighter the coloration of the plant, the higher the light intensity it needs to be provided. The following species can be attributed to this group of plants, arranged in order of their predisposition to bright light: A. splendida, A. reineckii, A. lilacina, A. sessilis.
Alternanthera reineckii
«1» South America. This is a very beautiful plant with a long stem and pink-red or dark-purple leaves. Its branches and leaves can creep along the water surface and grow quite long. Height 15–40 cm. Width 10–15 cm. It grows slowly, but under bright lighting, it is very decorative. It forms a green, sometimes reddish, creeping stem with aerial roots and an upright top. The upper part of the leaf is green, the lower part is pink or reddish. The stems of the plant grow perpendicularly and quickly reach the water surface, and in shallow aquariums (up to 20–25 cm), they even grow above its surface. Aerial leaves develop on the stems that have reached the water surface. In this case, the functions of underwater leaves lose their effect, and the plant sheds them. Alternanthera grows all year round. Among the imported species of Alternanthera, A. reineckii is the least demanding (but, unfortunately, also the least decorative) plant. There are several garden forms:
— Alternanthera lilacina hort. The root system is poorly developed and consists of a single cluster of thin, delicate roots. The stem is straight, long, herbaceous, round, brownish-purple in color. Leaves are simple, lanceolate, arranged in pairs opposite each other, with each pair perpendicular to the next pair. The upper side of the leaf ranges from light to rich brown, the lower side is bright purple. Petioles are shorter than the leaf length.
— Alternanthera “Osiris” (A. osiris hort). The root system is poorly developed and consists of a single cluster of white, thin roots. The stem is long, straight, round, herbaceous, green in color. Leaves are simple, arranged in pairs opposite each other. Each pair is perpendicular to the next pair. The upper side ranges from tender green to rich green with a yellow coating. The lower side is green, sometimes with a crimson coating. The plant can form shoots from the root base. When trimming the top of the plant, stem shoots easily develop from the leaf axils. The plant prefers soft, clean water. More suitable for the aquarium and more decorative.
— Alternanthera sp. rosaefolia. A very attractive long-stemmed plant whose leaves range in color from pink-red to dark-purple. Very bright lighting is required for Alternanthera. It is precisely the nature of the lighting that determines the coloration of the leaves and the appearance of this plant.
— Alternanthera sp. splendida. An erect, elongated stem up to 50 cm high. Leaf arrangement is opposite. Leaves are ordinary, short-petioled or sessile. The leaf blade is bright red, sometimes purple or lilac.
— Alternanthera reineckii “Grunblattrig”. Leaf is about 10 cm long and up to 2 cm wide, upper side is olive-green, lower side is brownish, leaf edge is often ruffled.
— Alternanthera reineckii “Rotblattrig”. Exceptionally similar to the previous form, but the upper side of the leaf is red-brown.
— Alternanthera reineckii “Lilablattrig”, formerly called Alternanthera lilacina. Leaf length from 7 to 8 cm and width up to 2.5 cm, without ruffles on the edge. The upper side of the leaf blade is red, the lower side is red-purple.
«2» The plant will feel comfortable in a tropical aquarium with a water temperature of about 24–28 °C. When the temperature drops to 20 degrees, its growth slows down significantly. The plant tolerates both slightly acidic and slightly alkaline water reactions well. Water hardness and acidity do not matter unless there are extreme deviations. The most suitable pH is 7, dH 4–12°. It reacts negatively to increased hardness; net-like leaves, deformed and twisted ones may appear, and growth may stop. The same phenomena can be caused by the excessive accumulation of waste products from aquatic inhabitants, which clearly indicates the need for water changes, up to daily ones (about 15%).
It is advisable to change the water constantly, as this plant loves fresh water; in old water, it usually slows down its growth. Lighting is bright; leaf coloration depends on it. With an abundance of light, the front side of the leaves is bright green, and the back side is light green or pink. Shaded bushes bear leaves with an olive-brown upper surface and a violet-red lower surface. If the lower leaves begin to rot while the stem is healthy, this is always associated with a light deficiency. A large amount of light is necessary for growth and to preserve dark-red leaves. The daylight hours should be at least 12 hours.
«4» Its root system is quite weak, containing weak outgrowths at the base of the stem and numerous adventitious roots in the leaf axils. Moderately nutritious substrate from 2 cm. Substrate siltation is not of great importance for Alternanthera. Alternanthera receives nutrients mostly directly from the water. The nature of the substrate is also not of great importance for it, but in coarse sand, its root system develops somewhat better. Mineral supplementation brings considerable benefit during rapid plant growth. It should receive a good amount of nitrogenous substances as well as trace elements. Ferrous iron salts should be added to the aquarium water 1–2 times a month, at 0.1–0.2 mg per 1 liter of water.
«5» This plant is good to use for planting in the background in small aquariums; it looks better in groups. It is also suitable for planting in the central part of the aquarium. Since the leaves of this plant are quite rigid, you can not worry that aquarium fish will ruin them. Such plant will look wonderful if planted on the side ledges of the aquarium. The plant should be planted in such a way that its tops are located close to the water surface. As they grow, its runners will rise up, become heavier, and lower the plant.
The top of the stem that has reached the water surface should be pinched in a timely manner. This operation not only ensures the preservation of underwater leaves but also forces the stem to branch, forming highly decorative bushes that change their color depending on environmental conditions. Its vegetation is slow and requires good lighting and a rich substrate. Alternanthera reineckii grows best in a humid greenhouse. Fully submerged in water, it develops very slowly.
«6» It is propagated by stem cuttings and root shoots. Cuttings should be left to float, and they will quickly form roots, after which they can be planted in the substrate. During the period of intensive growth, a piece of a densely foliated stem 10–15 cm long can be cut off and planted in groups of 3–5 pieces directly in the chosen place in the aquarium. It is better if this place is located in the midground, in front of taller plants of green or yellow-green color.
Fine-grained, nutrient-rich substrate is best for initial planting and rooting of the sensitive stem. Rooting usually occurs within 10 days, but at first, the growth of young plants is often significantly slowed down. For planting in the aquarium, cuttings from fairly large stems should be used. There should be at least 4 pairs of leaves on the cutting.
Identification: Alternanthera reineckii
Alternanthera reineckii lilacina, rosaefolia, Alternanthera sessilis
Echinodorus “Red Diamond”, “Red Flame”, “Rose”, “Rubin” 
