Duckweed

About

Duckweed (Lemna minor) is one of those plants every fishkeeper eventually has an opinion about. Usually strong, and often shaped by experience cleaning it off a skimmer or filter intake. Each plant is little more than a tiny, flat green oval, sometimes with a single hair-like root dangling below, floating freely at the water surface. What it lacks in size it more than makes up for in ambition: under good light and with nutrients available, colonies can double in a matter of days, forming dense green mats that shade out whatever is below. In the wild it turns up on still and slow-moving freshwater across much of the world, including wetlands and lagoons in South America. In the aquarium it has genuine uses. It pulls excess nitrates and phosphates from the water, provides cover and shade for surface-shy fish, and makes a nutritious live food for goldfish, cichlids, and other herbivores. The challenge is managing it rather than growing it; once introduced it rarely leaves completely. For a species as simple as a few cells and a root, it asks almost nothing of the keeper, making it one of the most beginner-accessible plants in the hobby, assuming you are ready to stay on top of it.