I've used fishbowl discussions before but not inconjunction with TBL (other than the grade weight setting exercise). I kind of liked doing them but found the students resistant to the technique at times. The best strategy for me was to have the students prepare answers to several questions beforehand (what was something you thought you could use in the chapter... what was something you found consistent with your experiences... what was something you found inconsistent with your experiences, etc) and use those questions for their conversations in the fishbowl. Perhaps some of their resistance was due to their lack of preparation (pre TBL) and it would be different after a RAT or in response to a problem that the teams had solved. I haven't tried it yet (still pretty new to TBL). Karla