My 30ltr tank is running since October, all was good with no major drama until about 5-6 weeks ago when algae took over. My wife liked to feed the fish and let the lights run for ~ 10h a day, the algae mended her ways.
Drastic action caused the algae to disappear but the water remained cloudy so for the last 2-3 weeks I change ~ 30% water (10ltr). However, there is white foam floating on top with lots of brown algae (yesterday changed 13ltr and cleaned the plant's leaves with paper but today it looks as I did nothing). The water parameters are good, 0 ammonia, 0 - 0.25 nitrite, nitrate was not tested but the tap water are at 40ppm. I can't see the nitrite climb drastically in 2-3 days period.