I was wondering if anyone had any advice as to what types of water plants I should put into my 1/4 acre pond. I have two aerators and it is generally in good shape, but last year I had a really bad infestation of what I believe was watermilfoil. The good thing was, my pond had never been as clear. Bad part was that it just completely took over the entire pond. I killed most of it using diquat as trying to rake it out would just make it grow faster, but what I would ideally like is some plant life that will provide some of the same water clarifying benefits but isn't as aggressive. I had heard that hornwort, narrow and broad leaf arrowhead or eelgrass are all good. I just don't know how aggressive/effective they are.

I like to dabble with pond plants and have found that the most reliable way to find plants that will thrive in your pond is to look at the ponds near your area. If a certain type of plant grows out of control in a local BOW...chances are that it will in your BOW, likewise for the opposite. If you do not see any native arrowhead in older established public waters (or otherwise), chances are it will not do well in your waters.

There are exceptions, but it can be costly and take time to find out what those are with trail and error by buying plants online and giving them the season to prove themselves.

The arrowhead in my pond is a blessing. They are tropical looking, bloom nicely, and don't grow in water deeper than a foot or so. They are a little unsightly once they die back in the fall, but the dead matter can be cut and removed from the pond if you catch it before it turns to mushy matter and start to float about and sink.

I have a Water Hyacinth experiment going this year that may be of interest to you if you are looking to put some work into it to remove plant matter once it pulls the nutrients out of the water.
I can't say much about their effectiveness in my region just yet, let alone further north.

Here;s the thread...

http://forums.pondboss.com/ubbthreads.php?ubb=showflat&Number=508366&page=1

I have narrow leaf arrowhead starting to get a good grip on my banks. They are very prolific in the deep south. Also just invested in 5 sets of hybrid water lillies. They grow in shallow water and dont spread too aggressively. Planted them about a month ago and they are doing really well. If you get really cold winters, you'll have to set them in pots so they can be removed and kept inside, tho. Also have a nice spread of wild Iris. This was the first year they bloomed and seeded out so next year will be interesting to see how well they expand. Would love to have water hyacinth, but that's a recipe for disaster down here.

A word of caution...if you decide to do some transplanting, keep them isolated for a month or so to make sure you're not adding something else that may be piggybacking in the roots. Clean the roots as much as you can without damaging the plant before planting. My Iris has had a few strands of alligator weed trying to grow out of it. I pull up every strand I find. That stuff is very aggressive down here too.