Phycomycin is a non-copper sulfate based algaecide. It’s typically used in ponds with koi, trout and goldfish. Basically when dissolved in water it forms hydrogen peroxide which then kills the algae. That hydrogen peroxide then out-gasses to the atmosphere and it’s gone. What’s left if calcium carbonate which then sinks to the  bottom of the pond. Frequently used in drinking water reservoirs.