This worked for me but I dont have any fish in my pond presently (thanks to visiting critters). I had a horrible snail problem and they were chewing up the waterlily pads as soon as they hit the surface. The string algae was a bit annoying but a toilet brush helped control that. Anyway, found some copper sulfate crystals and dropped them in the pond. End result: snails are gone, algae gone, plants okay. That was two weeks ago.
Solution for algae/snail problem.
Where did you buy copper sulfate crystals? My father in law is looking for some and has had a difficult time finding a source.
Isn't copper sulfate the same as that tree root killer that you pour down the drain? I think it is, but I will check the label when I get home tonight and let you know.
I finally found it at a nursery. It was cheap, just 3-4 bottle. It does look like the crystals you pour down a drain. Anyhow, I got it to kill the snails that are in the pond by the hundreds. They were demolishing a lily pad the day it came up. Dropped a few dozen crystals into the bottom, snail gone. I did not realize it but apparently it gets rid of string algae too. Water is crystal clear with no string algae. Funny. Didnt hurt the regular plants though. I dont think I would use it if you have fish though. Apparently, it has already disapated because there are a bunch of frogs in the pond.
There are a number of fish medications that contain copper, so it is safe for them at some concentrations but I have no idea how strong those are.