Pond Boss Forums AQUATIC VEGETATION Controlling unwanted plants Pondweed

American Pondweed aka long leaf pond weed. Amer. pond weed is great pond plant and great habitat for fish as long as it does not cover more than 25%-30% of the pond shallow water areas (littoral zone).
How big is the pond???
As esshup says granular herbicide is good for spot treating some areas to kill back the pondweed so it is not so abundant to initially and quickly open some areas to fish.
If it were mine, I would this Spring add a low number of grass carp (white amur) to eat some of it and thin it out - reduce it - so not as much is present. Initially GC are slow to get it noticeably reduced the first year. GC are MUCH easier to add than remove!!. A good benefit of using GC instead of chemicals is they eat it to produce manure to feed the good phytoplankton and zooplankton community to create more plankton turbidity to help NATURALLY shade out the deeper growing pondweed. Go slow with adding extra GC as they need to be 1.5 - 2.5 yrs old to see their affects on effectively reducing the pondweed. I think 3 or 4 GC per acre can eat at least 3-5 pickup truck loads of Am pond weed per year converting it to plankton fertility depending on size of the GC. Ideally you don't want pondweed growing deeper than 6-7ft.

Pond dye can help reduce the depth that the pondweed grows. Remember you really DO want some pond weed present - due to its numerous benefits. Use according to label or slightly less. I would first start with blue dye then later blend in some black with the blue. Black dye is mostly blue with some red and yellow added to get the darker black shade.

I think the best way to start with your Amer. pond weed infestation is a good combination approach. Use some granular herbicide early in the program for some quick partial weed reduction, add an appropriate few GC, add some pond dye. ALL depending on the size of the pond, Initially for the first year, manually removing some of the pondweed is also a very good idea. Less chemical to mess with, give the GC time to eat and grow, dye shades the deeper growing weed, and ALSO manually removing some gives you good exercise, garden mulch and pond activity observing the status of the pond. Manual removal will better educate you on the extent of the problem so you see the success progress over the next few years. A Lake Rake with rope and a Weed Razor are very good tools for manual weed removal methods to have in the Pond Tool Box.

Again how big is the pond?
How deep is it? and
How clear is the water? Amer.pondweed tends to make the water clearer so it can grow deeper.
REMEMBER you always want some Amer pondweed to compete against Filamentous Algae and you have fewer problems with FA.. Actually the more pondweed you have the Happier the Water Quality is for growing fish.