I set up my 30 gallon tank with approx. 30 lbs of live rock 4 weeks ago and am still showing significant ammonia levels. Is this normal? The tank smelled really bad and the water was very dirty looking for the first week, but for the past 3 weeks it has been crystal clear and no smell. And yet my test kit says there is still ammonia in my tank. Is there anything I can do to speed up this process?