About the best way to get rid of nitrates is with water changes unless
you have plants. Nitrates are not as toxic to fish as ammonia or
nitrites so you are not necessarily facing a panic situation.

Is the ph of your tapwater normally 6.2 or did you add something to
bring it down? What kind of fish are you keeping? Many species do
well in that ph.

Mark
http://www.cichliddomain.com