With the water temps as cool as they are you are probably OK. If you see a lot of fish cruising the edge of the bank that wont hit a lure then you could have the start of disolved oxygen sag. If you have an aerator then I would turn it on to keep the disolved oxygen levels up for the fish at least for the next few days. Copper Sulfate does work well on filmentuous algea but it also kills the macrophytes that are beneficial to the fish.