A little more than a year into the new pond and am having some veggie problems.. I am pretty sure this is small pondweed.. (Corrections to that identification are obviously welcome!).. I have also had an issue with FA and difficulty getting a decent bloom going..
I have never fed the pond, it does not get significant leaf drop, there is NO runoff into the pond, I top it off with well water... I'm having trouble getting my head around where the nutrients are coming from.. And I need some guidance on how to control this veggies..
Your plant is likely one of the several types of small or narrow leaf pondweed. It is often one of the first rooted plant invaders in new ponds. Nutrients for its growth are coming from the pond bottom clay/soil.
aka Pond Doctor & Dr. Perca Read Pond Boss Magazine - America's Journal of Pond Management
For long term control I would first try chemical free control - white amur aka grass carp. I often suggest stocking just enough fish to eat 1/3 - 1/2 of it and manually remove 1/4 and leave 1/4-1/3 as competition to filamentous algae. You get rid of all the pondweed and FA will want to replace the same amount of biomass with FA string algae. FA is harder to deal with IMO than narrow leaf pondweed. Some pondweed is very good habitat in the pond.
aka Pond Doctor & Dr. Perca Read Pond Boss Magazine - America's Journal of Pond Management