Azolla filiculoides (aka Water Velvet) is a miniscule floating plant. From a distance it can resemble Duckweed (Lemna minor), due to both having tiny leaves, but the plants are unrelated. In fact Azolla are more closely related to Salvinia. Both are floating, aquatic ferns. This fast growing plant will sprout daughter plants from the parent plant, creating mat-like layer of plant material on the water surface. Like Salvinia, its leaves have a fuzzy, velvety look to them. This comes from the many tiny, water repelling hairs that grow on the leaf surface. Unlike Salvinia, Water Velvet does not grow trailing roots. In a warm body of water with bright lighting, A. filiculoides can take on a rusty red color.
Care Level: Easy
Preferred Water: pH 5.0 to 7.0, Soft
Minimum Lighting: Moderate to Bright
Temperature: 59°F to 79°F (15°C to 26°C)
Leaf Size: Length, 0.75″ to 1.25″ (1.9 cm to 3.2 cm)
Water Velvet traditionally hails from North America, primarily in warmer regions, as well as parts of Asia and Australia. It can be found in slow moving bodies of fresh water, such as ponds or lakes.
Water Velvet spreads simply through division. The mother plant sprouts attached daughter plants, which in turn sprout daughters of their own. Under favorable conditions, this plant can spread incredibly fast. According to plantrescue.com, Water Velvet has “a surface-area doubling time of 7-10 days under favourable conditions.” This means that Water Velvet can cover the surface of a pond faster than many other plants can compete with. Like other fast growing floating plants, this can result in plants below the surface being starved of light.
In the Aquarium
Water Velvet is a lovely, easy to care for floating plant. Like most surface dwelling plants, water agitation is a factor to consider. As with plants like, Amazon Frogbit and Common Salvinia, gentle water flow is preferred, and if flow is too tumultuous, the plant may not survive. Because it grows so quickly, it may need to be thinned frequently to prevent it from blocking light and gas exchange at the water surface. surface-dwelling fish like gouramis and killifish will appreciate the cover provided by this plant, and unlike Salvinia, Frogbit, or Water Lettuce, this plant does not have trailing roots that will “clog” the water below.
Water Velvet is very tolerant of lower water temperatures. In areas with mild winters, this plant can be kept in outdoor ponds all year round. If the water surface is frozen, this plant is able to survive for up to a week or more, though any plants frozen above the water line will certainly perish.
Re-evaluation of Species Classification
Until recently, many have improperly classified Azolla filiculoides as Azolla caroliniana. There has been some confusion, combining Azolla filiculoides and Azolla cristata as Azolla caroliniana. Research conducted by Evrard & Van Hove in “Taxonomy of the American Azolla Species (Azollaceae): A Critical Review” (2004) has distinguished these species, based on observations of the trichomes on the surface of the leaves. They are unicellular in A. filiculoides but septate (two-celled) in A. cristata.
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Featured image credit: Kurt Stüber. Source: Wikipedia.org