Gentlemen,
The weeds in my 1.5 acre pond are becoming a problem. I was hoping somebody could give me their best practices.
I did some searching here and think I have an answer for most of the questions you guys typically ask. I also grabbed some pictures of the problem weeds. I think they're southern naiad, but I'm deferring to your expertise.
As of today:
PH: 9.0
Ammonia: .25ppm
Nitrite: .25ppm
Phosphate: 0.0ppm
size: 1.5 acres
avg-depth: 9-10 feet (13' for most of pond, with 30 degree banks and a 4' shelf along one shore that's overrun with cattails)
water-source(s): ground water seepage/runoff
water-uses: fishing/swimming
fish present: LMB/BG
static or transitioning water (degree & frequency): largely static, can close off the floodgate if needed
% of weed-coverage: 20% of pond, 100% in swimming area
are any other desirable plant species present?: cattails for BG cover, but they're getting excessive

I'd like to completely eradicate the suspected naiad from the swimming area, which is about 100 X 40 with a 4' average depth. Am I best off treating with Sonar AS, or is there a better Sonar for my situation? Possibly some other herbicide is a more suitable option? I was also reading about Spiritflo, which seems to have the same percentage of fluridone although I can't be sure of the other contents.

After a day of "mechanical removal" that I'm pretty sure will spread the naiad later this summer (and also left my legs screaming), I'm open to any ideas!

Thanks!
czimmerm

Your pictures of plants outside water are a little fuzzy, but I think your plants are Chara - technically it is an algae. Clearer, sharper pictures would help. Best chemcial for Chara is Cutrine-Plus granular or some similar buffered(cheleated) copper granular. Verify it is Chara before using Cutrine. If your weed is Chara, Sonar(fluridone) will not affect it.

I prefer a "lake rake" or beachcomber rake for moderate infestations and grass carp or tilapia when the plant gets too abundant for practical raking. Both fish will eat Chara.

Thanks Bill. I can stop and try to get better pictures tomorrow. I should have mentioned that I thought chara too, so I tried the sniff test. It doesn't have that distinctive smell I'm told chara has.

Sago pond weed maybe? I am battling that in one of our BOWs last year and this year. Diquat is good. Go to "The Pond Guy" web site and email a (clearer)picture to them. Their email is weedid@thepondguy.com

They will quickly get back to you with what it is and how to control/kill it. BM61.

I've uploaded a clearer pic from this afternoon. Hopefully it'll help with your diagnosis.

Thanks BM61. I've uploaded a better pic. I'll give the guys at The Pond Guy a shout if all of the PB folks are out doing summertime stuff, and to see what they can sell me for chemicals.

The clearer picture indicates Chara aka musk grass - technically an algae but it looks like a submerged weed. If your water is soft with low alkalinity then you likely have Nitella not Chara; similar to Chara but prefers softer water which you could have in MN. Use management methods mentioned above for Chara. They can be considered a beneficial plants for fish habitat and cover. I don't like them because they usually form black anoxic sediments underneath the beds unlike most submerged aquatic plants.

Thanks again Bill.
Is it possible that chara doesn't smell at some point during the season, or if the water's still cool?

Next question: am I helping to spread the stuff by raking it out? I've been trying to come up with a cable-towed rake solution between two shorelines. I figure if the nesting bluegill can keep it down, maybe an automated solution will work.

Chara reproduces vegetatively and sexually. Vegetative reproduction takes place by tubers, amylum stars and secondary protonema. The fructifications for sexual reproduction are globule or antheridium (male) and nucule or archegonium (female). I suppose plant fragments with the right structures can regrow. Some sources say not to rake Chara which will cause it to spread, but West Chester Univ and The Academy of Natural Sciences, Philadelphia say: "....musk grass (Chara), and mats of filamentous algae are easily raked up onto shore where they can be dried and collected for disposal or composting. Chara will quickly decompose and leave a brittle white residue, so it should be removed more quickly."

There are many species (abt 90) of Chara. Some may not have the characteristic odor of Chara vulgaris. I am not aware of an odor by Nitella species.

This from the web:
Chara is a multicellular algae that resembles a vascular plant because of its stem like and leaf like structures.  Chara can form thick, dense mats on the bottom of your waterbody.  It does not have roots, but its branches grow into the sediment to form a loose connection between the colony and the bottom substrate.  Chara provides essential food and habitat to other aquatic organisms.  It is an efficient filter and greatly improves water quality.  However, Chara can grow to a nuisance level quickly and can be tamed with algicides or mechanical removal.

Seems high to me but I am not a pro. I would be interested to see what the pros have to say....

Perfect! Thank you!
I'll pick up some Cutrine-Plus granular and get the rake moving to remove the dead mass after it does some damage.

Those figures had caught my eye too, but I'm faaaaar from knowledgeable.

The pond was dug in the summer of 2009, and I tested the water in the spring of 2010. The only change in water measurements since then was that the nitrite level went up from 0 to .25 ppm. I was thinking that I may be getting too large of a fish population to drive that number up?