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Aquarium floating plants are chosen less for their appearance than those growing in the main body of the tank, and more for their function. They provide spawning sites and food for many fish species, and also give cover and help to diffuse harsh aquarium lighting. Floating freshwater aquarium plants vary widely in both size and leaf shape, and some grow on land as well as in water. Currents in the tank have a marked effect on the distribution of floating plants, so you may have to adjust the filter outlet to achieve an even spread.
- 1 Here Are Some Of The Best Floating Aquarium Plants
Here Are Some Of The Best Floating Aquarium Plants
Water Lettuce (Pistia)
- ORIGINS Abundant in waterways in tropical and subtropical parts of the world.
- SIZE Leaves can be up to 4 in (10 cm) in length.
- WATER Temperature 72–86°F (22–30°C); soft (50–100 mg/l) and around neutral (pH 6.5-7.5).
- PROPAGATION Break off the plantlets that develop on the stem-like stolons.
The leaf clusters of this floating plant are lettuce-like in appearance. The tiny flowers emerge in the axils, between the leaf and stalk, while the trailing roots—which extend down to a depth of 30 cm (12 in) – may be used as spawning sites by some egg-laying fish. Good lighting is vital for the successful spread of the plant, which grows fast under favorable conditions. Prevent condensation from dripping on to the leaves because the plant will rot.
Azolla caroliniana (water velvet)
- ORIGINS From the U.S. to South America; introduced to Europe in the 1870’s, and now found wild in some areas.
- SIZE Leaves each measure about 0.5 in (1.5 cm).
- WATER Temperature 68–86°F (20–30°C); hard (100–150 mg/l) and around neutral (pH 6.5-7.5).
- PROPAGATION Reproduces asexually, so simply divide an existing clump.
Azolla caroliniana can appear bright red under intense lighting, but more usually it will be bright green, as seen above. This plant will soon spread over the surface of an aquarium and is a useful supplement to the diet of vegetarian fish. It also provides support for the nests of bubble-nesting species, such as gouramis, and serves as a retreat for fry, which may find food among its trailing roots.
Amazon Frogbit (Limnobium laevigatum)
- ORIGINS From Mexico through Central America to Paraguay in South America.
- SIZE Leaf diameter is 1–2 in (2.5–5 cm).
- WATER Temperature 68–86°F (20–30°C); soft (50–100 mg/l) and around neutral (pH 6.5-7.5).
- PROPAGATION Split up existing plants; the divisions will grow rapidly.
The rosette-shaped leaves of Amazon Frogbit are paler underneath and sometimes display dark markings on top. They are able to float thanks to their spongy, air-filled structure, which gives them a slightly swollen, convex appearance. Aquarium strains are female, and although they flower quite readily, there is no likelihood that they will set seed in the absence of the male flower’s pollen.
Butterfly Fern (Salvinia auriculata)
- ORIGINS Found widely in waterways from Mexico south as far as Paraguay in South America.
- SIZE Leaves are 1 in (2.5 cm) long, 0.5 in (1.25 cm) wide.
- WATER Temperature 64–77°F (18–25°C); soft (50–100 mg/l) and around neutral (pH 6.8-7.2).
- PROPAGATION Simply break up the branches formed by this fern.
This is another species for which bright lighting is very important. If the tank has a glass cover, it must be tilted slightly so that condensation droplets do not fall on to the ferns, because this will cause the plants to rot. It may occasionally be necessary to thin out the growth because Butterfly Fern can spread rapidly into a dense mat that will prevent light from reaching other plants beneath.
Duckweed (Lemna minor)
- ORIGINS Found throughout the world in both temperate and tropical regions.
- SIZE Leaves are small, measuring about 0.2 in (5 mm).
- WATER Temperature 41-86°F (5–30°C); soft (50–100 mg/l) and around neutral (pH 6.5-7.2).
- PROPAGATION Split off a few pieces from a mat; they will soon start to replicate
Duckweed grows under a wide range of conditions, even in an unlit aquarium, provided that it receives some natural light. This floating plant is a useful addition to a rearing tank and can serve as a food source for vegetarian fish. If there are no plant-eaters to keep its growth in check, remove some of the duckweed with a net to prevent it from choking the surface.
Watermeal (Wolffia arrhiza)
- ORIGINS Found throughout the world, in both temperate and tropical regions outside polar areas.
- SIZE Tiny leaves measure about 0.05 in (1 mm).
- WATER Temperature 59–82°F (15–28°C); soft (50–100 mg/l) and around neutral (pH 6.5-7.5).
- PROPAGATION Split off a few pieces from a mat; they will soon start to replicate.
Watermeal is the smallest flowering plant known. Although the genus Wolffia comprises eight recognized species, they are all very similar in appearance. Watermeal is easy to grow, with its green coloration turning reddish under bright light. A ready supply of trace elements in the water will encourage rapid growth.
Liverwort (Riccia fluitans)
- ORIGINS Another widely distributed species, occurring in parts of the Americas, Asia, and Europe.
- SIZE Leaves typically no more than 0.08 in (2 mm).
- WATER Temperature 68–82°F (20–28°C); hard (100–150 mg/l) and around neutral (pH 6.5-7.5).
- PROPAGATION Break off a piece from an existing clump to add to a new tank.
Liverwort differs from other floating water plants in that it grows just below the surface, where it ultimately forms large balls. It can also be grown out of water in damp mud. It will thrive under relatively hard water conditions in the aquarium. Liverwort is especially valuable in tanks housing livebearers, providing fry with a safe refuge from the predatory attentions of other tank occupants.
Water-sprite (Ceratopteris thalictroides)
- ORIGINS Grows widely throughout the world’s tropical regions.
- SIZE Up to 24 in (60 cm) tall when rooted.
- WATER Temperature 72–86°F (22–30°C); soft (50–100 mg/l) and slightly acidic (pH 6.5).
- PROPAGATION Young plants develop on the edges of existing leaves.
This is one of the most versatile of all aquarium plants since it can either be rooted in the substrate or float on the surface. When allowed to float, it has a more flattened appearance, with the leaves appearing slightly broader, while the white roots simply trail down in the water. Water-sprite’s coloration is variable, depending not only on the lighting conditions but also on the levels of dissolved nutrients in the water.
Bright lighting is essential if it is to thrive, but if the illumination is too intense, the leaves may become scorched and dieback. Water-sprite is not a long-lived plant, being effectively an annual. Mature leaves produce buds that ultimately give rise to new plants. These may be separated from the parent plant once they are about 1.5 in (4 cm) across, but they can also be left to detach themselves. They will then float up to the surface and develop there naturally, sometimes protruding above the waterline.