no ammonia spike?

[Puffer22]

started up a 56g a month ago. it now has about 15lbs (so far) of live rock and 2lbs of live sand (plus the 3in we started with). recently we added a few hermits and have had a few snails emerge from the live rock. the problem is the ammonia and nitrites. the tank has been tested since the beginning and both ammonia and nitrites have been at 0 and haven't changed. is something wrong? why is there no ammonia and nitrite spike in the cycle?