Several questions about care for fresh water tank?

Update: I have a 55 gallon aquarium. I have a constant algae problem. I purchased a uv filter which took care of the green algae but brown algae starts to show up after a month of cleaning. What to do?
Update 2: I have a under gravel filter, is this necessary anymore? I have a duel outside filter that I change out the cartridges every month.
Update 3: I do not over feed my fish.
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