Duckweed is a hardy floating aquatic weed that can become a problem if not kept in check.
It has small oval leaf like fronds that bud from the base and a single root that hangs in the water. It grows extremely fast and soon spread to form a carpet on still water. It produces tiny white flowers that are so small they are rarely seen.
Although it is an excellent food source for goldfish, if left to cover the water's surface it can take all the sun away from the plants below the surface causing death of those plants.