I concur, Chara. Duck food? What ducks are supposed to eat it, coots? I've seen it growing in 2' deep water, and it is just shy of the surface. FWIW, if you want to control it, it's best to start when it's <6" tall in the spring, and most algacides will treat it. It's not a true plant, is a form of algae.

www.hoosierpondpros.com

[Linked Image from lh6.ggpht.com]
http://www.pondboss.com/subscribe.asp?c=4
3/4 to 1 1/4 ac pond LMB, SMB, PS, BG, RES, CC, YP, Bardello BG, (RBT & Blue Tilapia - seasonal).