What's eating my ceratophyllum demersum?

Hornwort (Ceratophyllum demersum) is a fast-growing submerged plant for aquariums and ponds. Its bristly texture deters most grazers, but goldfish, koi, and waterfowl will eat it in ponds. Algae is a lesser concern as hornwort outcompetes it, but aphids can attack emergent tips in outdoor settings. Fish grazing is the main threat.

Fish eat and shred soft growing tips, stripping the plant rapidly in ponds Use a separate pond or exclude fish from the plant zone; provide alternative food

Birds pull up and eat large sections of floating hornwort in outdoor ponds Cover small ponds with netting; plant in submerged baskets to reduce accessibility

Clusters on emergent or surface tips cause yellowing and distortion Submerge tips briefly to dislodge aphids; introduce natural predators outdoors