We have a 29G tank that has been going for about 2 months now. We have several groups of different kinds of tetras. All is well, ammonia at 0 and Nitrates are at 10-15. We feed them once a day and the light is on for about 6 hours a day. We clean the gravel once every 2 weeks and do a 30% water change at that time. We have floss as one of the filter media and that is changed once a month and we clean the sponge in tank water once a month. We continue to get brown algae on our plants and the one statue in the tank. Not much on the glass other than at the bottom near the gravel. Is there anything else we can be doing to prevent the brown algae?