Subclass Alismatidae
Order Alismatales
Family Alismataceae
Genus Helanthium
Helanthium bolivianum
Transferred to the genus Helanthium in January 2009. Synonyms: Echinodorus bolivianus, Echinodorus angustifolius, Echinodorus austroamericanus, Echinodorus intermedius, Echinodorus magdalenensis, Echinodorus quadricostatus, Echinodorus xinguensis.
«1» Native to central South America, Costa Rica, and Cuba. This species differs significantly from other members of the genus in appearance, recognized primarily by its very narrow leaves, often only 2-3 mm wide. It belongs to the smaller Echinodorus species, sometimes referred to as the Pygmy Amazon Sword. The submerged form has lanceolate-elongated leaves with a cuneate base and a more or less pointed apex, sitting on a short petiole.
The leaf blade is bright green and translucent, with a clearly visible central vein and an irregular transverse pattern. The leaf has a very short petiole, 10-12 cm long, typically 6-10 cm in an aquarium, and the width does not exceed 3 cm at its widest part. In a shaded aquarium, they reach a length of 20-25 cm. The plant rosette produces a large number of oblong green leaves whose blades gradually widen from the base upwards. The leaves are very fragile.
«2» The temperature for good growth should be 25-28°C. It prefers regularly changed medium-hardness water and moderate lighting. Stable growth is observed only in neutral to slightly alkaline water. Acidic environments inhibit plant growth, causing it to become severely stunted. In moderately acidic water, well-developed plants are never produced, foliage is poor, and leaves frequently disintegrate at the edges. At pH below 6.5 and above 7.5, leaf tips break down.
In hard water and with excess light, it shrinks to 2-3 cm in height and reproduces poorly; infrequent water changes also halt growth. In a well-lit location, the plants are relatively short (up to 10 cm); in shaded areas of the aquarium, they are approximately twice as tall. Insufficient lighting leads to premature leaf decay. Lighting should be provided for at least 12 hours.
«4» The thickened rhizome holds firmly in the substrate. This species is undemanding regarding substrate composition. A 3-4 cm layer of substrate ensures proper root system development. It tolerates excess organic pollution well and is well suited for planting near fish feeding areas. Excess food decaying on the bottom in these areas does not affect this species at all, whereas with other plants, this often causes rotting and dropping of leaves. In an established aquarium, natural silt accumulation provides sufficient nutrition. Very pale leaves indicate a lack of nutrients.
«5» It is relatively hardy and grows evenly in the aquarium year-round. It forms quite dense thickets in the aquarium. It grows strongly and rapidly and is recommended for beginners. It is an ideal plant for carpeting large areas in the foreground of the aquarium. In large and deep aquariums, it is primarily used for planting in front of large rocks in the middle ground.
This plant features characteristic light-green leaves that contrast nicely with darker plants in the aquarium. The designated area is planted with spacing of 5-8 cm apart—within two to three months, they grow so densely that no ground space remains for new plants, causing new shoots to grow straight up so that the roots of young plants stretch downward through the water column. This looks very effective and enhances the aquatic layout.
If runners are prevented from spreading by pinching them off, the bushes will grow larger with more leaves. The plant readily produces runners spreading in various directions. To maintain the group within a specific zone, runners should be trimmed and replanted elsewhere. To create a compact group, their spread should be restricted by rocks or other objects. In semi-shaded conditions, it forms a light-green, delicate, and fairly tall growth that usually reaches the water surface. It can be kept in heavily stocked fish tanks. The plant is undemanding, tolerates transplantation quite easily, rapidly forms new leaves, and practically does not shade the aquarium.
«6» The plant reproduces via runners. It multiplies significantly faster than Echinodorus tenellus. A single chain of stems produces up to 10-15 young plants, while the mother plant and already well-rooted young specimens simultaneously release new runner stems. Each new stem grows upward and then lays down; after the first young plant appears and roots, subsequent stems creep horizontally. Runners are detached from the parent plant when reaching a length of 30-50 cm. Young, fast-rooting plants grow on each of them at intervals of 5-10 cm, capable of forming solid thickets within a few months.
Later, their roots turn green, making detached and replanted young plants less likely to establish successfully. Therefore, root runners should be pressed down to the bottom so young plants root directly in the substrate and develop independently. Detaching plantlets without damaging the runners is difficult, so the runner is cut into sections, each retaining one well-formed plant with 5-6 leaves. Due to the production of numerous long runners, the mother plant becomes heavily depleted, leaving it with only 3-4 leaves and reduced aesthetic appeal. Therefore, after sufficient propagation, excess runners are recommended to be trimmed.
Helanthium tenellum
«1» Transferred to the genus Helanthium in January 2009. Synonyms: Echinodorus tenellus, Echinodorus brasiliense, Echinodorus ecostatus, Echinodorus parvulus, Echinodorus subulatus. Common name: Pygmy Chain Swordplant. Distributed from the southern US states to southern Brazil and the Antilles. The smallest plant of the genus. A very popular aquarium plant forming dense thickets of compact, bright-green rosettes of elongated, petioleless leaves. Leaves are linear, pointed at the ends, straight or curving sideways and backward to form a neat rosette, up to 8 cm long and no more than 3 mm wide. Leaves are green, turning ruby-red under bright lighting.
It is an acaulescent herbaceous plant with greatly elongated, lanceolate, petioleless leaves gathered in a rosette. The plants resemble small grass tufts. Plant height is typically 5-6 cm, with older clumps occasionally reaching 10 cm. Shortly after transplantation, small plants begin producing basal runners that creep along the substrate surface, forming new young plantlets at nodes spaced 1-3 cm apart. Vegetation continues year-round.
This species has several varieties. — E. tenellus var. tenellus. Leaves are ovate with an ovate-expanded base and strongly tapered apex. Variety — E. tenellus var. parvullus (dwarf). Leaves are regular lanceolate, narrowed at the base and ending in sharp tips; petioles are 2-3 times longer than the leaf blades. — Echinodorus tenellus rubra — distinguished by narrower leaves and a prominent central longitudinal line. Depending on light intensity and other health factors, this line is pinkish-red under optimal conditions, while under lower light it is typically light green.
«2» The plant is undemanding regarding maintenance conditions. Water temperature can fluctuate within a very wide range, from 18 to 30°C, with optimal conditions at 24-26°C. Preferred water hardness is above 4°. In very soft water, older leaves quickly disintegrate. It performs slightly better in neutral to slightly alkaline environments. It can be grown in water with hardness from 1 to 14°dH and pH 5.5-8. Regular water changes are recommended.
An important factor for successful cultivation is intense lighting. Strong illumination is required. Only with sufficient light will it form a dense carpet in your aquarium. Under bright light, the plant acquires vivid coloration, and the clumps remain short and compact. Under insufficient lighting, leaves stretch upward and turn a pale greenish-yellow. Photoperiod can range from 11 to 14 hours depending on fixture power. It is very sensitive to short winter daylight hours and bottom silt accumulation. To keep its thickets bright green, dense, and beautiful in winter, plants should be illuminated for approximately 12 hours.
The main difficulty in cultivating this species is its intolerance to algae fouling on the leaves and debris accumulating among the small plants. Algae growth can be prevented by proper lighting choices, and debris should be regularly removed with a siphon during partial water changes. Even if it appears dead, new shoots will inevitably emerge near the roots after some time.
«4» The plant develops slowly in new, nutrient-poor substrate and rapidly in heavily silted substrate. Coarse sand is the best substrate. In coarse-grained substrate, the root system develops poorly, and thickets become uneven. When planting in new substrate, no extra additives are needed; gradually accumulating silt provides sufficient nutrition. Substrate layer can be minimal, 2-3 cm. Mineral supplementation is required only in densely planted aquariums.
«5» Foreground thickets of Helanthium tenellum wonderfully decorate the aquarium. It grows equally well in shallow and deep water. Under favorable conditions, it develops and propagates normally at depths up to 50 cm. Plants should be placed in well-lit areas. In a short time, dense, light-green thickets form, hiding the substrate entirely.
When carpeting large, flat, or slightly sloping bottom areas, ensure plants are spaced evenly, 3-4 cm apart. This ensures rapid and uniform coverage within 2-3 months. A defined patch of green carpet can also be achieved by using narrow acrylic dividers pressed into the sand 1 cm above the substrate. Plant a few specimens inside this enclosure. As runners cross the boundary, cut them or turn them back inside and weigh them down with pebbles. Planting density: 6-7 plants per 10 cm2.
It pairs well with Lilaeopsis brasiliensis due to their similar leaf shapes, creating a smooth transition between species. Carpeted areas should be siphoned every 1-2 weeks depending on fish load. Neglecting this causes decaying fish waste to accumulate, potentially killing the plants, especially in lower areas. It suffers greatly from algae overgrowth and trapped debris, which makes the lawn look messy.
«6» Each tuft rapidly produces 2-3 runners bearing consecutive young plants. Such a runner with 2-3 daughter plants can be detached and replanted elsewhere. Under favorable conditions, young plants establish quickly, forming a new thicket in 1.5-2 months. Daughter plants grow from underground runners. They should be left attached to the parent plant temporarily until reaching half the size of the parent, after which runners are severed to allow independent growth.
Identification: Genus Helanthium
Echinodorus cordifolius schlueteri, “Leopard”, “Ovalis”, “Marble Queen”.
Synonym table for the genus Echinodorus. 
