Pond Boss Forums AQUATIC VEGETATION Controlling unwanted plants Small private pond with weed problem

My family lives up the hill from a small private pond in Canton, CT. It's had problems with large mats of weeds every season and in the past 10 years it's almost gotten out of control where maybe 50% or more of the pond is affected.

Grass carp were introduced years ago and some are almost 3 feet in length now and the problems have not lessened. I've yet to determine exactly what species of weed is growing, but I believe it to be either Elodia, Millfoil, and possibly Hydrilla (though I guess hydrilla is very rare in CT.)

I've thought of proposing using Sonar or another similar product since the carp seem to be having less of an effect than was promised. My question about that is the pond seems to be fed by underground springs and there is a small runoff spillway or dam about 4 feet across that has a small flow of water year round. Would that lessen the effect of Sonar or another herbacide?

Also in my reading about treating millfoil types, there has been much talk of using the insects called Weevils to destroy populations of millfoil. Is anyone here familiar with Weevils and there application to combat weeds?

I will follow up with a definite identification of the plant as soon as possible.

-Keith

Grass carp lose their effectiveness as they age. A 3 footer actually eats less than one that is half its size. I think I would eliminate the existing ones and stock some younger, more active ones. You haven't mentioned the size of the pond nor the other fish.

Keith,

Don't know about the insects, but can comment on the carp and Sonar. Yes, water flowing out of the pond will effect Sonar. It is slow working and could be potentially severely impacted by water flows. We have a resident expert, Kelly, who hopefully will comment further.

I've observed a definite drop off in grass carp effectiveness after three years in my Texas ponds. They need to be rotated out and replaced every three year by younger grass carp.