I’ve dosed 5x the recommended amount and let it sit until the next day before water changing it out to kill algae before I don’t know what kind of plants you have but I had Java fern and frogbit in the tank the Java fern seemed to be unaffected but the frogbit did suffer quite a bit but was not killed off completely and I also did remove the fish before hand I did not want to risk them over dose at your own risk but it did kill the algae