Hi, Recently I've noticed this brown/dark yellow spots on the glass, bottom of aquarium and on the leaf of plotted plant. I rubbed it off some times ago and it's back again. My guess is it's a brown algae..could you guys have a look? Size: 20 gal Time: Having for over 3 months Fish: I've 2 fish and 2 fries and do bi-weekly water change (30%). Location: My aquarium is near the window and it gets direct sunlight for couple of hours daily.