Pond Boss Forums AQUATIC VEGETATION Controlling unwanted plants Why in My Pond? (Duckweed)

Boy am I glad to find this site! Seems like all the others that I could find only pertained to 100 gal. garden ponds.

My 3/4 acre pond is almost 5 years old now and for the last 3 1/2 years I've had a duckweed problem. Normaly, I'll skim the surface once a week (all summer)and scoop out probably 80% of the weed and a week later the pond is completely covered again. I'm hesitant to use any chemicals for fear of harming my fish (catfish, crappies, perch, hybrid sunfish) or my snails, clams, crayfish, etc.
Nobody else in the area seems to have this problem. What is it that makes my pond such great duckweed habitat and is there anything I can do to eliminate it and not harm my fish? I'm at wits end and about ready to drain the pond and start over. Help!

small ponds tend to have big problems with duckweed. if you have any livestock in the watershed that will compound the problem. your fear of chemicals is unjustified, you need to apply fluridone to eradicate the duckweed. diquat works well for killing the duckweed fast but usually will not eradicate it.

draining the pond wont work, you will have to treat with fluridone (sonar or avast) to get rid of this problem

Hi Shan and thanks for responding.

There are no livestock in my watershed. I have used fertilizer though, because without it the water is clear and blooms are rare. I also have a real problem trying to keep the ph balanced; my watershed mainly consists of a hemlock bog and the water that flows out of it and into my pond (which only happens after heavy rains, snow melt) is very acidic. Something about my set-up is very conducive to the production of duckweed.

Tyler - I'll second Shan's comments, but add a footnote about fluridone's use.

Your pond needs to be static [no flow-through] for at least 30 days after a fluridone treatment - preferably longer - for the the product to be fully effective. If that isn't likely, topical applications of REWARD [diquat] may be your only remaining option, and will require repetitive treatments to gain the upper hand.