Water Lettuce (Pistia stratiotes) is a freshwater, floating plant. Outdoors it can grow to a diameter of 12 inches or more, and is able to grow dense mats with fuzzy, pale green leaves. It has long trailing roots that can reach as long as several feet.
Care Level: Easy
Preferred Water: 6.5 – 7.2 pH – Soft to Moderately Hard
Minimum Lighting: Moderate to High with some available shade.
Temperature: 65 to 84 °F (18-29 °C)
Leaf Size: up to 6 in (~15.2 cm)
Water Lettuce was first discovered in Africa, however some fossil evidence is claimed to show it has long existed in southern North America. It’s origins are uncertain, but it currently can be found in many regions of the world. In the U.S. it is considered an invasive species in Alabama, California, Connecticut, Florida, South Carolina, and Texas.
Water Lettuce, like frogbit, reproduces primarily by way of runners which sprout daughter plants. It does produce miniscule flowers between its leaves, but this is an unlikely form of reproduction in the aquarium environment. According to Florida Fish and Wildlife Conservation Commission, under ideal conditions this plant can double in population within three weeks.
In the Aquarium
Water Lettuce is a fast growing plant. It is great for absorbing nitrates from the water. Its long, feathery roots offer excellent shelter for fish fry and microorganisms.
As with fast-growing floating plants like frogbit or salvinia, it can quickly cover the aquarium surface and other plants growing below it.
As an Invasive Species
Water lettuce can quickly form large expanses of dense floating mats at the water surface and shade out native submersed plant species. These mats can also cause problems for humans and other animals by blocking up otherwise clear waterways. Like other floating plants it can prevent adequate gas exchange and the water surface.