I wish I had your property. I'd love to have an acre pond! I have a couple of much smaller earth ponds, and they are real fun to have. You can easily grow pondweed, which will soon take over your pond. Or you can plant pond lilies, which will probably spread much less rapidly. I don't think hyacinths do well in the north at all--they died in my ponds, maybe because I put them in too early in the year, or perhaps because the wind simply blew them onto shore. Duckweed did the same thing to me, although it grows quite well in the area on some ponds. Everything here in my area of W. WA seems to be lilies. Good luck. I also envy your pond depth. I only have 6' of depth.
Randy

parrot feather will do great did for also lillys just get the hardy ones

Herons wiped out all my fish. I've seen both a blue heron and a green heron on my ponds. They are "stealth" predators. When I had a dog, my fish survived. When I no longer had a dog, my fish died. With a pond your size, you might need to provide lots of cover. I went ahead and let some invasive plants in, which may have been a mistake. I'm now thinking of throwing some old stumps back in the water, to provide hiding places. Good luck!
Randy

I live about 60 miles north of Albany.

For free-floaters, water hyacinth and water lettuce do well here once the frost is over, which means June. Another plant that is a floater that works well is azolla (fairy moss). There are others like frog bit, but I've never tried that.

Good luck. A one acre pond sounds delightful.
Anne

Check with your local DNR for illegal plants. Maybe they have a list of recommended plants. There are a lot of websites by State Universities with Cooperative Extension Services that have suggestions for maintenance of large ponds but there are not many that name good plants. Sorry, I lost the list when I changed to a new computer. DH neglected to transfer my documents files and my memory is shot since I had surgery. I can't remember specifics of so many things. I vaguely remember Ohio State had a site and I am pretty sure Michigan State did as well but I think there was a phone call involved.

Hybrid hardy waterlilies are just about the only game in town for a pond like that, they will cope well with the 4'-6' deep area.

There are different growing habits among the hardies, odorata hybrids are often dumped free or cheap by contractors looking to stick you with a hefty pond clearance bill down the road, those are pondbusters

Any waterlily source worth their salt will have a selection of medium to large Marliac hybrids which are well suited to the task, modest spreading rates, very pleasant bloom to pad ratios

Water hyacinth might work well, if there is a suitable sheltered bay that warms some, those would need to be raked and thinned out when the first frosts scorch them

Those make good winter fodder when left to dry out, if you have grazing critters about

Water Hyacinth, Water Lettuce, Parrot's Feather, Duckweed --all incredibly invasive.

I like mosaic, with tight patterns of red and green leaves. It does fine just floating on my ponds, but I read it's supposed to be rooted in soil.

It grows rapidly here in the tropics, don't know how aggressive it is where you are.