This is because moving animals can unknowingly transfer wildlife diseases and invasive plants between ponds ... duckweed ...

Duckweed is a tiny, free floating green plant that can form thick blankets across a pond. Duckweed an important food source for birds and wildlife and it has such good water filtering capabilities ...

Spirodela polyrhiza, the most ancient member of the duckweed family ... Duckweeds—tiny plants that float in ponds and lagoons—have evolved to become increasingly simple and to reproduce ...