09-23-2012, 02:18 PM
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If the brown algae is diatoms, this is common in new tanks (during the first 2-3 months). It is easy to remove from plant leaves using your fingers. Most of the algae-eating fish will relish this stuff, though I am not suggesting buying more fish just for this; but if you happen to have otos, bristlenose, farlowella, and such, they will eat this. But it should not reappear once the tank is biologically stable.
Although light has little effect on diatoms, i do agree that you should reduce the duration, or you will have green or red forms of algae and they are much more difficult to deal with. Light duration should balance the nutrients available for the plants, and no more; then the plants use the light and nutrients, and algae is unable to take any advantage. It is difficult to say about duration in new tanks because everything is unsettled biologically and algae will often appear just due to this. I tend to start with a reasonable period, say 8 hours, and monitor plant growth and algae. If green/red algae appears, reduce the duration. You can go as low as six hours.