Never heard of crystal plex. Is it some form of copper sulfate? If so is, your water quite hard? If that is the case normal copper sulfate will have little effect. It could be you need to wait somewhat also.

Curtrine plus works better in hard water and it could be an option if this one does not work out. I use a net, duck taped to an alluminum pole that is sold at a local Bait and Tackle for spearing fish. I have filamentous algae for about a month and a half max in spring and then the chara dominates and uptakes the nutrients. I don't find the Chara to be too much of a problem but will be introducing grass carp as they like chara.

If pigs could fly bacon would be harder to come by and there would be a lot of damaged trees.