GC are one of those things that either you have too many of them and all the weeds are gone or you don't have enough and wonder if they are present at all. It is very difficult to find a happy medium with GC.

If it were me I would skip the GC and use pond dye late in the fall prior to ice up and then freshen it up again in the spring at ice out. Curly leaf pond weed likes to start growing when the water is still relatively cold right after ice out when the water is still too cold to use herbicides. Plant growth is like a three legged stool, plants need nutrients, light, and the right temperature to take off and grow. Take any one of those three away and they won't do well. Limiting the available light for photosynthesis with a conservative amount of pond dye is probably the easiest way to limit plant growth in your pond.