What's eating my lemna minor?

Common duckweed (Lemna minor) has few true pests — its biggest threat indoors is heavy algae growth that competes for light and nutrients in still water. In aquariums, goldfish and koi eat it voraciously, and some aquatic snails rasp fronds. Outdoors in ponds, ducks graze it deliberately. Maintain good water flow and remove excess algae manually.

Outcompetes duckweed for nutrients and light; thick blooms mat over the fronds, causing them to yellow and die. Reduce fertiliser input, increase surface agitation, and manually remove algae; UV clarifiers help in recirculating systems.

Fronds consumed rapidly; a single koi pond can strip duckweed cover within days. Separate duckweed into a tank or trough without large fish; float a mesh cage on the pond surface to protect a breeding colony.

Fronds rasped and fragmented; large snail populations can reduce cover noticeably in closed aquarium systems. Hand-remove excess snails; introduce assassin snails (Clea helena) to control populations in aquarium setups.