Hi, Algae build-up is dependant on Nitrate and Phosphate levels; temperature, pH, hardness, and dissolved oxygen readings; as well as light intensity and duration, which is why it's one of the worst problems a fishkeeper faces - the causes are really complicated! As for your set-up, I would need to know a bit more about the readings I specified above - nitrate is the main one in freshwater tanks. If this is above 50 parts per million, then that could be your problem, and the solution is much less food and a few decent-sized (30-40%) water changes over a period of a few weeks (assuming your tapwater is low in nitrate). Otherwise, it could be your light period - often, algae can be cut right down by having a dark period in the middle of the day (i.e. turn the lights off for about an hour at lunchtime or thereabouts). The light shouldn't be on for more than 12 hours a day - 9 or 10 is more accurate for coldwater tanks. Algae has always been a bane of aquarists' lives, so don't despair - persevere and you will beat it! Good luck!