add some live rock 1-2 lbs per gallon. This will help stabilize the water quality, create nooks and crannies for beneficial organisms like pods that eat the fish waste, and are free snacks for the fish. That way you don't need to feed as often.
If possible, add a fuge with cheato. They make HOB fuges.
You must also think about phosphates. Nitrates and phosphates do NOT always go hand in hand and phosphates alone can make algae grow like crazy. There are two ways to lower phosphates: a phosphate reactor and/or a fuge with cheato.