Your system is large enough to provide some forgiveness, however, your biological filter bed has not matured well enough to support much of a bio load at this point. you did not say, but I assume you did observe a cycle on the system. anyways, next should be the clean up crew. you might get away with adding one fish and wait two weeks between additions and look for a slight cycle in the system. My advice is to add nothing to the system until your parameters are constant and good for at least 3 months at this point. (beware of the new tank syndrome if you load up too quickly.) now is when the patients is needed to go slowly and read the helpful articles. there is information there to help you on stocking your system. good luck, be patient, and keep us posted. happy fishin.