You know, I stared at the screen for about ten minutes trying to figure out what to say here. There are some posts in this thread that just make me laugh . . . but anyway.
:notsure:
Adding a chromis is fine . . . you are not going to hurt anyting at this point. A chromis is a rather hardy fish that will survive the cycle if it occurs at this point. Granted while I do think that you should have made sure that your tank has fully cycled, I dont feel that you made some grave mistake by adding it.
Add your inverts when you start to notice an algae outbreak. Since most invertebrate animals will not tolerate levels of ammonia, you must make sure that the tank is stable and cycled before you add them. Using a test kit is really the best way to tell.