In Praise of Vallisneria

Included among the various species of Vallisneria are some of the most adaptable and easy to keep plants available to the aquarist. Rarely expensive, and usually sold in even the smallest stores, Vallisneria are easy to obtain and settle into a new aquarium quickly without going into ‘shock’ as many Cryptocoryne and Echinodorus species seem to do. They do not need special substrates enriched with laterite or loam, and they are not picky about water conditions, doing as well in slightly brackish water as they will in an ordinary freshwater community tank. In a centrally heated house, some species will even do well in unheated aquaria with coldwater species. Unlike many aquarium plants, they are able to extract the carbon dioxide they need for photosynthesis from the carbonate salts in the water, so systems for adding carbon dioxide to the water aren’t important either. All they really require is bright lighting, but that doesn’t mean you have to spend a fortune on expensive metal-halide or mercury vapour lamps; two or three ordinary fluorescent lights that run the full length of the hood will do the job, providing you aquarium isn’t more than 50 cm deep. In short, Vallisneria are excellent plants for the beginner and advanced hobbyist alike.

Species of Vallisneria

There are any number of species and varieties of Vallisneria, and telling them apart is not easy. Many dealers sell them under variety names, such as ‘torta’ and ‘red tiger’ that don’t really mean much from a botanical point of view. Fortunately, the commonly traded Vallisneria all have much the same requirements, so it doesn’t matter too much which ones you decided to buy; simply choose the varieties that you think will look nice in your aquarium and suit your budget. The following are the most commonly traded species, arranged in order of size, starting with the smallest.

Vallisneria tortifolia (twisted vallis)

Vallisneria tortifolia is a dwarf species with tightly coiled leaves. Compared with many other Vallisneria species it is a bit delicate and needs good lighting, but it is otherwise a good choice for small tropical and unheated aquaria. Because of its small size (it rarely grows taller than 20 cm) and its bushy, twisted growth, this plant works better as a mid-ground plant rather than a background one.

Vallisneria spiralis (straight vallis)

Despite its Latin name, the leaves on this species are not particularly twisted compared to some of the other Vallisneria, and so this is one instance where the common name is quite helpful. It is a versatile species that adapts well to both unheated and tropical aquaria, and will do well under moderate lighting, though like all Vallisneria it does best in brightly lit tanks. The leaves on Vallisneria spiralis can grow to lengths of around 40 cm, though many specimens stay much smaller than this, and is an excellent choice for planting the background of small and medium sized aquaria. It is debateable whether plants sold as Vallisneria spiralis are actually that species; according to Baensch’s Aquarium Atlas, plants sold under this name are in fact more likely to be Vallisneria asiatica.

Vallisneria spiralis variety torta

Although you will see this name quite a lot, the proper name of this plant is Vallisneria americana. It is similar to Vallisneria spiralis, but is much more variable. Aquarium strains tend to be relatively small (maximum height of around 40 to 60 cm being typical) and having somewhat or very twisted leaves. Wild specimens can be straight or twisted, and can get much larger; leaves of lengths of over 150 cm are not unknown!

Vallisneria asiatica (Asian vallis)

Vallisneria asiatica is similar to Vallisneria spiralis, except a little larger, with leaves up to 60 cm long being typical. Hardy and tolerant, it prefers unheated, strongly illuminated aquaria but will adapt to tropical aquaria with only moderate lighting without fuss. A good all-rounder, its fast growth and deep roots make this species an excellent choice for use in aquaria with fish that do a little digging, such as dwarf cichlids, gobies, and Corydoras catfish.

Vallisneria americana variety biwaensis (corkscrew vallis)

Vallisneria americana var. biwaensis has the size of the Asian vallis but with twisted foliage like that of Vallisneria tortifolia. Although tolerant of water conditions and temperature, Vallisneria americana var. biwaensis will not grow under poor lighting, and is probably the most demanding of all Vallisneria in this respect.

Vallisneria gigantea (giant vallis)

Vallisneria gigantea is not the correct Latin name of this plant, but it is the one it is traded under; most of the plants sold under this name are in fact specimens of Vallisneria americana. The giant vallis is a fast growing species, and will reach its full size remarkably quickly, mature plants being able to grow by as much as 1 cm per day. The leaves are thick (2 to 3 cm across) and extremely long, easily exceeding lengths of 100 cm.

Vallisneria gigantea variety rubra (red giant vallis)

Vallisneria gigantea variety rubra is another probably dubious name that has attained widespread currency in fishkeeping circles. More than likely it is actually a variety of Vallisneria americana or Vallisneria neotropicalis. It is similar to the giant vallis in looks but is noted for its rather reddish foliage. Just as easy to keep, but needs good light.

How to keep Vallisneria

First, be sure and pick a species suitable for the size of tank you have. Vallisneria spiralis, for example, will work better in a small tank than Vallisneria gigantea. If you want to use these plants purely to fill the background, then you will need species that are about as tall as the tank is deep; so for the average beginner’s tank that is 30 to 45 cm deep, Vallisneria spiralis and Vallisneria tortifolia will fit the bill nicely. On the other hand, if you want to create a canopy of floating leaves that will be appreciated by fish that like shade, such as killifish, catfish, Ctenopoma, and many cichlids, then taller species of Vallisneria are more appropriate. Species that are two or three times taller than the tank is deep work well, and ideally what you want is to position the plants close to the flow of water out of the filter so that they drape across the surface of the tank attractively.

As mentioned earlier, Vallisneria are not picky about water conditions, and unlike many aquarium plants they do well in hard, alkaline water. In fact, they do not seem to do well in soft, acid water at all. Vallisneria are also among the few aquarium plants that tolerate brackish water, and if gradually adapted to increasing salinity, will tolerant a specific gravity of at least 1.003 without complaint, making them an excellent choice for use in tanks with gobies, livebearers, and other brackish water fish.

Good lighting is important: none of the Vallisneria described here will do well in tanks with only a single fluorescent tube. On the other hand, two tubes should work well, especially if you install reflectors behind the tubes to maximise their effectiveness. Do remember that the deeper the tank, the more lighting you will need, and in very large tanks (more than 50 cm in depth) you may need to opt for higher output lights such as metal halide and mercury vapour ones.

Generally speaking, Vallisneria will do well in plain gravel but even better in gravel that has been enriched with loam or laterite. Either way, these are ‘greedy’ plants that need regular feeds of iron-rich fertiliser, of which there are numerous aquarium-safe varieties.

Planting and pruning Vallisneria

Many aquarists fail to keep Vallisneria alive, and almost invariably it is because they have neglected two absolutely key rules. Firstly, never bury the roots deeply. Vallisneria hates to have the top of its root system underground, and the crown of the plant, the part where the leaves and roots grow from, must always be 1-2 cm above the surface of the substrate. The crown is easy to spot; it is usually whitish, or at least a very light green, compared to the rest of the plant. The easiest way to plant Vallisneria is to make the hole in the gravel or sand with your fingers, and then push only the lower part of the root system into it. Pack the sand or gravel around the roots, taking care to keep the top of the roots and the crown of the plant clear.

The second golden rule is to make sure the leaves are never snapped or bent. Once this happens, the leaf will die. A common problem is small pieces of gravel getting stuck between leaves at the base of the plant, and over time the gravel causes the outermost leaf to fracture, leading to the death of the leaf. This problem is best avoided by making sure the plant is not buried in the substrate too deeply, so that gravel cannot fall into the crown.

A widely held myth among aquarists is that Vallisneria cannot be pruned. This is not true; they can be pruned, but it needs to be done carefully. What is essential is that a sharp knife is used to cut the leaves cleanly and without starting fractures running down the length of the leaf. Should that happen, the leaf would start to decay. Alternatively, over-long leaves can be pulled away at the base, where they will quickly be replaced with new growth.

Propagation

Once settled in and happy, these plants will rapidly spread out across the tank by sending out runners bearing daughter plants. After a few weeks the daughter plants will lay down their own root system and the runner can be cut, and if necessary, the daughter plant can be moved to another location.

Other issues

The leaves on these plants are quite long lived, and because they float at the surface they can quickly become covered in algae. Plecs and other catfish from the Loricariidae family will help, but the bigger catfish find sticking onto the rather thin leaves of Vallisneria difficult, and may in fact cause damage while trying. More agile species, like flying foxes and black mollies, work rather better. Otherwise, simply crop or remove leaves that have become unsightly.

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