Short of an extreme circumstance, I would never recommend Algaefix. It's a sledgehammer approach to a killing algae, with the side effects you're seeing.
In order to address your problem, we need to know more about your situation. What kind of algae is it? How old is the tank? What kind of lighting do you have? What are your actual water parameters? "Perfect" unfortunately means nothing to us, as different people have different definitions of perfect, and often people that report their water as "Perfect" only say so because an employ at a fish store told them that, and not because they measured the parameters themselves.
Algae creates 75% of the world's oxygen, so really we're all just doing our parts...