I'm seeking advice for a friend of mine. He's had his planted tank set up for at least a month now. Prior to that, it housed turtles. It's a 30 gallon tank with a 2-bulb, T-5 HO, 6500 K bulb lighting fixture. The lighting cycle runs 12 hours a day. He doses carbon excel and has a DIY carbon diffuser made using yeast in a milk jug. He is having a brown algae issue that he just can't seem to shake. It's covering his gravel, rock and plant leaves and it seems to be getting worse. Any input? Thanks you.