I probably noticed within a week or so. Takes a keen eye though, like noticing a lot of baby polyps popping up under the bigger ones. And seeing polyps pop up out of a mass of bubble algae that over took a frag and was tossed to the side of the tank thinking it was gone. If everything goes right you should just notice overall better health in the polyps, hard to explain but you can just look at them and tell they are living life.