Currently restarting a new tank (60 gal) - has been totally cleaned out and has been fishless cycling about 2 weeks now and tested the water yesterday at the aquarium shop. They said ammonia was very low but should be zero. My question is how is there any ammonia in the tank with no fish? If the ammonia is so low, can I add fish to the tank again? The other stats were normal except for the general hardness was too low. I have added more salt to help this. Is that correct?