Your tank is somewhat new. The older it gets, the more "stuff" that grows to help lower nitrates. Microscopic bacteria. Algae on rocks, sand etc Others please help or correct me if I'm wrong I'm new too. The older my tank gets the more my nitrates go down they are finally 0. I did it with mainly PATIENCE with aging, more lighting to get dark spots growing algae, water changes and adding a nice sized refugium. Until 6 months from now.....you must do 20% water changes frequently no slacking. There is no other POSSIBLE way to reduce until your tank is aged like a fine wine. Wish I could speed aging of wine or fish tanks I'd be rich. I'm not yelling the capital letters are for importantce the other suggestions are also great i wont repeat. +2 love this site