my tank has been cycling for almost two weeks now (11 days to be exact) my ammonia is at zero (has been for the past 4 days) , but the nitrite hasn't budged at all (up or down). is this normal? if so, when should i expect it to start dropping? I have a 24 gallon tank with a 3'' bed if live sand and about 19 pounds of live rock. Thanks for the help!