Sometimes in Fish keeping it can turn out to be a spray and pray kind of thing. I would say the tank is better more water for him to dirty up. Fish die in tanks without BB because of bad water perimeters these can be removed with water changes so if you do daily changes you lower harmful levels of ammonia and your Rtc wont die (in theory this is the spray and pray part of it) Grab the stuff from your LFS or Petsmart and make sure you do a good water change before adding the stuff to max out the time its in there before a water change and to insure your not trying to balance water that is bad anyways.
Good luck I love Rtc's so i really hope this works out.
Ps: Ive cycled 5+ tanks with fish like Silvers Arow's Oscars, and other Cichlids without problem. Its not the smartest idea but it works in a pinch