[ChuckG]

Sounds to me like you are simply starting to "cycle". It's almost impossible to get fully cured rock that won't cycle on you to some extent. With this in mind, you mentioned that you were going to add more rock later on? I would suggest, if possible, to get all the rock you need now and put it in the tank. This way it will only cycle once. This should be done before adding any critters to the tank.