This aquatic plant is Watermilfoil. Underwater plants are good for ponds. They provide shade for the fish, protection from herons and kingfishers and food for the fish. EXCEPT... when the plant is watermilfoil - I have found out. Other underwater plants I've put in were all snarfed up by the fish so I was on the lookout for some more. I found a few sprigs of this plant by the Columbia River. I'll try this. BIG, BIG MISTAKE. Fish don't eat this. It is a noxious weed everywhere. It grows and grows and grows. It is damn hard to get out as it roots in the bottom and is brittle and prolific. It can grow from any little piece that is left behind. Today I noticed maple seeds sprouting and growing in it!!
Beware of what you wish for.... even Abby can't conquer this.