In my experience with Dempseys, I'd have to say that you'd definitely have problems. I've seen Dempseys go after Oscars that were big enough to make them look like fry. They just have a lot of pluck. That bichir is going to look like a giant worm to him. This is just my opinion, but like I've said, I've had trouble with dempseys, so I know how the bad end of the spectrum can be. The wife has more experience with Silver Dollars (assuming that's what you meant by SD), and she says she wouldn't reccomend the silver dollar as a tankmate. Even though she says it wouldn't be as aggressive as the Dempsey, she says fin-nipping could be a serious problem out of the SD.