Has anyone used Karmex/DF to control pond algae or have any other recommendations?

Copper sulfate is what I use. Never used Karmex DF. A cheap way we keep algae and pond weed off the top of your pond and to keep weeds down after treatment is to take a bundle of old copper pipe about a foot and a half long tie them together and submerge on the side of the pond where the predominant wind comes from. This little bit of copper slowly released does wonders

Be careful, you can't just kill all the weeds and algae in your pond. A bunch of rotting decomposing in your pond will suck the oxygen right out of it and kill your fish

Lake Madison in South Dakota, could use a semi truck load of it.

Spray ponds on the farm we pretty much keep clean as we can. Others we use for fishing and recreation and we use no weed control in them

Yup.......A fella hired someone to kill the cattails around the edge of his pond and killed some amazing bass, bluegills, and crappie. Very sad situashun.

If you want fish and you don't want vegetation you probably need to buy fish feed to keep them growing. You will also not have any good nursery type areas for small fry to feed on after spawning so that means frequent addition of fish and especially if you want some different year classes. If you don't have fish and you don't want weeds I would go to the lowest cost effective method you can find. Around here I would go to a large dairy that uses copper sulfate for their cows hoof baths and I would pour some and let the wave action distribute or you could get in a canoe and do a rough job quickly as well.

Bryce

To answer the original question. I have used karmex for several years. Typically we use it in the early spring. Although I’m not sure it is labeled for use in ponds or lakes.