About the Giant Vallisneria
Species Type: Freshwater Plants
Category: Substrate Rooted
Care Level: Easy. Adaptable, will tolerate soft or moderately hard water, low to medium light, some additional fertilization beneficial or necessary. pH 6.0 to 7.5, GH up to 15 degrees/260ppm.
Origin: Vallisneria gigantea is described as originating from Papua New Guinea and the Philippines, but the true species [see discussion] occurs throughout eastern and southeastern Asia, Oceania (Japan) and North and Central America.
Vallisneria, particularly the smaller "corkscrew" variety, have been popular and frequently-seen aquarium plants since the earliest days of the hobby. There is considerable confusion over the nomenclature of this genus [see comments below], and several different "species" and varieties may be encountered in the literature; one may therefore find the same plant under various names. The subject species is a case in point, and this will be discussed below.
This species, which may often be seen under the common name of Jungle Val and Freshwater Eel Grass as well as Giant Val, is the largest; some sources give 3-4 feet for the leaf length, but others including Kasselmann (2003) give 2.3 metres (7 feet). There is a wide-leaf (blade 10-25mm wide with 5-9 veins) and a narrow-leaf (up to 10 mm with 3-5 veins) form. Some regions consider this an invasive plant; in some jurisdictions such as New Zealand it is illegal to propagate, sell or distribute this plant.
Vallisneria plants are not particular about the composition of the substrate and will grow very well in plain fine gravel or sand provided liquid fertilizer is regularly added to the water. They readily assimilate carbon from bicarbonates (as opposed to carbon dioxide) and thus do exceptionally well in harder water; some can even tolerate brackish water that is not too high in salt. Several aquarists report that Vallisneria plants do not respond well to the use of liquid carbon supplements [such as Seachem's Excel and API's CO2 Booster] which are composed of the toxic chemical glutaraldehyde and water, and the plants completely melt.
Vallisneria species are quite similar in appearance to Sagittaria. The leaves of the latter are usually darker green and more stiff, pointed, and have a different vein structure; their roots are whiter and thicker than Vallisneria. Some aquarists hold that the two genera do not fare well in the same aquarium.
Vallisneria is distributed in all tropical and subtropical areas worldwide; in some places, such as the continental United States, they extend into the temperate zone. All species are dioecious, having male and female plants that both produce flowers. The female flowers grow on long scapes and float on the surface; male flowers are produced at the base of the male plant and become detached and float to the surface and open. The water then carries the pollen to the female flower. Seeds are not produced in aquaria, and the plants spread by numerous daughter plants that arise from runners. These daughter plants may be left to form an extensive mat of plants or separated once they have developed several leaves and roots and planted in another location.
The Hydrocharitaceae family of floating and submersed aquatic plants, commonly called the Tape Grasses, contains both marine and freshwater plants found on all continents in the tropical and temperate zones. With the exception of the Asian genera Blyxa and Ottelia, the plants in this family tolerate very hard water. All species are flowering, the marine species being pollinated submersed and the freshwater on the surface; pollen is dispersed by water except for Stratiotes and a few species in Ottelia that are insect pollinated. There are 18 genera, several containing plants commonly seen in aquaria.
The genus Vallisneria was named in honour of Antonio Vallisneri (1661-1730) by the "Father of Taxonomy" Carl Linnaeus (1707-1778) and he described the species Vallisneria spiralis in 1753. The confusion over the species in this genus has largely occurred due to the difficulty of identifying them by anything other than the flower structure. The leaves of plants in the same species can appear very different depending upon growing conditions, both in nature and in the aquarium.
The subject species was described under the name Vallisneria gigantea in 1912/1913 by Karl Otto Robert Peter Paul Graebner. According to the detailed work referenced in the following paragraph, this plant was believed to be Vallisneria americana, var. americana that was named by Andre Michaux in 1803. Notwithstanding the meaning of the species epithet, "from America," this species is found in eastern and southeast Asia, North and Central America, and Oceania (including Japan). The name V. gigantea was therefore a synonym, and this species is nevertheless widely seen in the literature under this name.
Studying the flower of each species is complicated by the plants having distinct female and male flower forms that occur very rarely in nature and are therefore difficult to obtain. Extensive research detailed in published studies in 1982 by two independent botanists, R.M. Lowden and Christopher D.K. Cook, came to the same conclusion: the genus Vallisneria holds only two species, V. americana and V. spiralis, and both have two varieties. The relevant taxonomic criteria to determine the true species turned out to be the arrangement of the carpels in female flowers and the number of stamens in male flowers. Since the vast majority of aquarists will not be familiar with flowering Vallisneria, detailing these distinctions here would serve little purpose, but there is a summary in Kasselmann (2003) for those who are interested. The plant endemic to Australia was determined to be Vallisneria nana by Jacobs & Frank (1997).
More recent work (Les, et al. 2008) using phylogenetics has resulted in 12 species being identified by molecular data, and an additional 2 or 3 species by morphological differences within groups that were invariant at the molecular level. Two new Vallisneria species (V. australis, V. erecta) are formally described in the same study.
Cook, Christopher D.K. and Ruth Luond (1982), "A Revision of the genus Nechamandra (Hydrocharitaceae)," Aquatic Botany 13, pp. 505-513.
Kasselmann, Christel (2003), "Aquarium Plants," English edition, Krieger Publishing Company, Florida.
Les, Donald H., Surrey W. L. Jacobs, Nicholas P. Tippery, Lei Chen, Michael L. Moody, and
Maike Wilstermann-Hildebrand (2008), "Systematics of Vallisneria (Hydrocharitaceae)," Systematic Botany, volume 33(1), pp. 49-65.
Lowden, R. M. (1982), "An approach to the taxonomy of Vallisneria L. (Hydrocharitaceae)," Aquatic Bot. 13, p. 293.
Rataj, Karel and Thomas J. Horeman (1977), "Aquarium Plants," TFH Publications Inc.
Ideal position in aquarium
A background plant that will continue to grow over the surface and significantly darken the aquarium if the leaves are not trimmed.
Moderate, but growth will be faster and stronger under brighter light.
Minimum Tank Suggestion
This species is only suitable for very large tanks, and especially useful in deep tanks such as cubes.
Ideal water parameters for Giant Vallisneria
This species will grow in medium soft to hard, slightly acidic to basic/alkaline water, though the plant will do best in in medium hard to hard water with a good flow. It usually does not do well in soft, acidic water. Temperature 20-28C/68-82F.