You should be testing your water EVERY DAY with a new tank and recording the levels. That's the only way you will know, and you need to know what your nitrogen cycle is like.
Plus if you havent done anything to add ammonia, the bacteria hasn't had anything to feed on to develop.
Please, please, PLEASE learn about the nitrogen cycle fully before you try to add fish. It will save you a lot of time, frustration, and money. There are probably sticky threads on this forum that have a ton of info on it. Heres a random site, too.
http://www.saltwater-aquarium-online-guide.com/nitrogen-cycle.html