Hello puffernet!
Just wanted to share this story with you all.  My friend keeps 3 big oscars in his 55 gallon.  They're about 7-8" or so.  One day he decided to get a Congo puffer and add it to the tank.  I'll have to say that neither of us knew very much about puffers, but the LFS said he'd be ok with the oscars, since he'd sit on the bottom.  Well, what the lfs didn't tell us is that these puffers are mean mean mean!  Upon adding Rambo (what else could we name him) to the tank, the oscars started chasing him.  We though he was a goner for sure.  Finally the oscars gave up and Rambo sat on the bottom, like the lfs said.  The next morning, one of the oscars was missing!  We thought maybe one of the other oscars ate it, but then noticed that one of the oscars had these half-circle chunks missing from its fins.  Needless to say, after about 3 weeks, Rambo lives by himself in a 55 gallon tank.  We were pretty mad at first, but had to say that was quite an impressive feat.  Now we keep Rambo well fed, and he lives with a pl*co named yuck.  We figured that's what he must taste like since Rambo hasn't eaten him yet!!!  Thanks for this site.  Todd