[Ebook] Encyclopedia of Aquarium & Pond Fish – Directory of Freshwater Plants – Floating plants

Directory of Freshwater Plants

Floating plants

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 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.

Water Lettuce (Pistia stratiotes)

• 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 stemlike stolons.

The leaf clusters of this floating plant are lettucelike 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 12 in (30 cm)—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.

Carolina Fairy Moss (Azolla cristata)

• ORIGINS: From the US to South America; introduced to Europe in the 1870s, and now found wild in some areas.
• SIZE: Leaves each measure about 1⁄2 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.

Fairy Moss 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 a 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, 1⁄2 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 1⁄5 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 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 1⁄25 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 1⁄12 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 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.

Watersprite (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. Watersprite’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 die back. Watersprite 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 11 ⁄2 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.