Fishless cycling?

This is your first time mentioned you get ammonia reading fro your tap water. Could you double check to make sure of it?

The ammonia in your tap water is more than likely ammonium. Ammonium is relatively harmless to the fish. To make sure it stay as ammonium, it is the best you use SeaChem Prime as your water conditioner. Prime can turn ammonia into ammonium for up to 48 hours. By then, your cycled filter system should have taken care of it.

Do not use RO water. It will cause more problem such as PH crash due to there is zero buffer.