Floating pond-cleaning plants help clear murky water. The nutrients (phosphates and nitrates) in the water are absorbed by the floating plants. The roots of the floating plants provide spawning media for aquatic life. Pond-cleaning plants help keep the pond clean, so that you do not have to use chemicals.
Water lettuce (Pistia stratiotes) is a perennial of the Arum family and is a floating water plant. It was seen as early as 1765 in Florida, and according to the University of Florida, it is not known whether the plant is native. The invasive plant resembles a floating head of lettuce. The leaves are light green, hairy, thick and rigid. The roots are light in colour and feathery. Water lettuce produces inconspicuous flowers. The plants must be in the water. The plants link together and form dense mats that are thick enough to hinder boat traffic. Water lettuce is not winter-tolerant. The water temperature must be 22.2 to 30 degrees Celsius; it will grow slowly in temperatures as low as 15 degrees C.
Azolla adds organic nitrogen to the pond, and helps to control weeds. It creates a mat that blocks out light, suppressing weed growth. It improves the soil quality at the bottom of the pond. Azolla is also used as a food source for farmed pigs, chickens, ducks and fish. It attracts duck in ponds, and ducks control the apple snail population. If the snail population is controlled, snail waste is controlled.
Water hyacinth (Eichhornia crassipes) is another perennial floating plant. It is native to Brazil. It is invasive, but if kept under control, it is a good plant to use as a pond cleaner. The plants vary in size, growing from a few inches to more than 3 feet in height. The lavender flowers grow in multiples on the stalks and add colour to the pond. The round, leathery leaves are attached to spongy stalks. The plants link together, forming dense mats in the water. The roots hang under the leaves and are dark purple or black. The water temperature must be between 25 and 30 degrees Celsius for optimum growth; water hyacinth will not tolerate water temperature over 35 degrees C or under 12.2 degrees C.