Subclass Magnoliidae ( Magnoliidae )
Order Ceratophyllales ( Ceratophyllales )
Family Ceratophyllaceae ( Ceratophyllaceae )
Genus Ceratophyllum — Ceratophyllum.
Represented by two species and one selective form “Mexico”. Plants are somewhat stiff to the touch, with a thin green stem and needle-like leaves in whorls (“Mexico” has dark green leaves and a red stem). Strongly branching. Under bright lighting, young leaves may acquire a reddish “tan”. Plants do not form roots and therefore do not need to be planted in the substrate. If you do not want them to float all over the aquarium, they can be fixed among stones or on a decor element. Domestic plant varieties do not withstand high temperatures (above 20°C).
Dark-green hornwort — Ceratophyllum demersum.
«1» (Eng. Hornwort). Hornwort is very widespread among aquarium hobbyists because it grows very quickly and is extremely undemanding. A long-stemmed plant with dark green needle-like leaves and reddish stems. It forms profusely branching stems (up to 1 m in length), the tips of which grow out of the water. Bush width is 5-15 cm. Leaves are arranged in whorls. The plant is very decorative, but has brittle and fragile leaves. Forked, bright green leaves resemble a horn in shape and hardness. — Ceratophyllum demersum “Foxtail” – Hornwort “Foxtail”. Differs from the usual hornwort in that its leaves are located closer together and it has many side shoots, which makes this plant compact and more attractive. More hardy and its stems do not break, unlike other varieties of Ceratophyllum.
«2» You can grow hornwort in any aquarium: cold-water, moderately warm, and tropical. At water temperatures above 25°C, the plant develops exceptionally fast. Moderately hard water with a neutral or slightly alkaline reaction is especially favorable for it. In soft water with an acidic reaction, hornwort grows somewhat worse. The plant needs fresh, frequently changed water. It does not like sharp changes in water parameters, which may cause it to drop its leaves. If this happens, you should separate the top of the plant and place it in the aquarium – over time, the hornwort will grow again.
When turbidity appears, its particles quickly settle on the hornwort and spoil its appearance. At the same time, the plant withstands the appearance of plaque and fouling on the leaves quite persistently. Special attention must be paid to light. Despite its dark coloration, the plant is quite light-loving, and the lighting must be bright. Natural diffused light is most beneficial for it. Under insufficient lighting, it grows poorly and becomes sickly. Algae rarely settle on its leaves. The duration of daylight hours should be significant, preferably at least 12 hours.
«4» This is a rootless plant, but it can be grown in the substrate. A root system is present in young plants; adults, as a rule, have no roots. Any substrate is suitable for hornworts. Hornwort does not need mineral fertilization. If you want to plant hornwort like a regular plant so it doesn’t float at the top, you can tie a bunch of stems to a suction cup and attach the suction cup closer to the bottom. Or tie it to a stone/driftwood, but so that the stems do not get trapped under the weight. You need to tie the hornwort carefully, without pulling the bunch too tightly – otherwise, you can cut the fragile stems with fishing line.
«5» Grows in the water column. You can plant both a whole plant and small twigs. It grows by 10-20 cm per week; with good lighting, the plant is able to grow at least twice its previous size in just one week. It brings benefits, especially in a newly established aquarium. While other freshly planted plants are recovering, rooting, and starting to grow, a strand of hornwort thrown into the aquarium immediately begins to grow and consume nutrients from the water that could otherwise become food for algae. It can be useful in the fight against algae because it cleans the water well of nitrates and releases substances that suppress algae. Hornwort leaves intensively clean the water by collecting the smallest particles that form turbidity, so it should be periodically rinsed in warm running water and placed back into the aquarium. Planting density – 5-6 plants per 20 cm2.
Hornwort thickets often become a good spawning ground for egg-scattering aquarium fish. As it grows, hornwort forms something like a ball in which fry and newborn shrimp can hide. In still water, growth slowed down significantly because in standing water, due to respiration and assimilation, a shell of weak carbonic acid forms around the plant, which slows down growth. At the same time, water movement should be just strong enough so that no carbonic acid shell forms around the plant. Too long stems can be pruned. In nature, hornwort is a seasonal plant; in an aquarium, it grows all year round under suitable conditions. In winter, hornwort usually dies off, leaving overwintering buds. When the water temperature drops to 12-14°C, the plant retains its apical buds, from which new stems develop in the spring.
«6» Hornwort propagates very easily by stem division. To get a new plant, it is enough to take a very small piece of the stem. A small side branch can grow into a large strand over time.
Submersed hornwort — Ceratophyllum submersum.
More beautiful than the dark-green hornwort. It differs from Ceratophyllum demersum in the following features: the species is more thermophilic, the stem and leaves are delicate, soft, green or brownish, which on the back side are sometimes covered with very thin teeth. Branches thrown into the water, unlike it, sink. Leaves are gathered in dense ring-shaped bunches sitting along the stem at equal distances. Each individual leaf is hard, horny, with short barbs, bright green, forked and branched. Whorl is 4-7 cm in diameter. All leaves are submerged in water and only the topmost ones protrude from the water.
Unpretentious, quickly adapts to environmental changes. Can grow in both soft and hard water. Feels great in tropical aquariums with a temperature of 25-28°C. Unlike many long-stemmed plants, it does not require bright lighting. Hornwort leaves have a remarkable property to purify water. The best way to maintain the beauty of this plant is, firstly, every time it reaches the water surface, cut it from the bottom and deepen it into the substrate so that its tip does not reach at least an inch to the surface, and secondly, change the water as rarely as possible and keep the aquarium as clean and far from light as possible.
In decorative aquariums, it is planted along the side or near the back walls. Compact thickets made of 15-20 stems look most picturesque. It can also be used as a free-floating plant. In low aquariums, it fills the water surface, significantly shading the lower horizons. To maintain the decorative integrity of the tank and prevent damage to other aquarium flora, hornwort stems must be regularly shortened.
Vegetates very quickly (linear growth can be 15-20 cm per week), actively participates in the metabolism of the aquarium, thereby acting as an excellent natural biological filter. The only, but significant drawback of this plant is the extreme fragility of the stems, which complicates its transportation and prevents its mass distribution in aquaculture. Propagated by stem division. It is enough to pinch off a small piece to get a new aquarium inhabitant. pH 6.0-7.5; dH 5-15°.
Identification: Genus Ceratophyllum — Ceratophyllum.
Eleocharis acicularis, parvula, vivipara, Cyperus helferi.
Lobelia cardinalis, Lobelia cardinalis “Small Form”. 
