betta i wouldn't trust..i've done it, but the betta didn't like it and got a bit narky towards it, mind you the bgk was as small as the betta.
dunno bout cories
most south americans are good as long as they are the same size
I had a partition in my 120gal with the bgk in one side and my barramundi in the other..
unfortunatly the aussies were to smart for they're own good and figured out if they hit the cover glass hard enough it would lift and they could jump over and get the bgk
mmm expensive dinner that was. remember bgks eat small fish too so anything that is small enough for it to eat will soon disappear..