I have a 7" M Blood parrot (did have 2), 4" F Con, 2.5" M? JD, 9" M Sev (did have 2) together with others in a 135, and have had no issues between any of them. The 2nd parrot that I no longer have died from complications after a pike smaller than she, tried to eat her head first and screwed up her gills and mouth, and the other sev I had to get rid of because he and my other sev went into ww3. But those problems had nothing to do with this combination. My parrot and con actually play as bouncers when others try to get in to scuffles. They come in and break it up.
