#glofish #algea #brownalgea #neontetra #help

I’ve had this fishtank for a few months (20 gallon with 5 GloFish Tetras and 3 Neon Tetras) brown has been growing on it and we did a water change cleaning the glass but it came back, can someone explain what this is and how to remove it? I wanna get rid of it before it harms my fish