Filter media meaning the blue sponge part with the carbon? I put a new one.So the new filter is part of it, coupled with two feedings a day. I get brown algae when the lights are wearing out, and green when they are on too long or the tank gets direct sunlight. You have both, which says nutrients to me.
I feed tiny amounts once daily, and skip a day once a week. Since I've been doing this, I've had healthier adult fish. Juvies get twice daily for growth.
Did you transfer your filter media when you started the new filter?