Reading this thread makes me sad over my clown knife. He was just over 22" when he died. I got him when he was only 4". He was 8 years old and at that time I didn't know it but I wasn't the best fish keeper.
I had him in a tank with 2 Oscars and 3 Parrot fish. I had him eating those alge discs and feeders. He ate 2 oscars and 2 plecos as well. I would have another again, but I would also try one of the other knifefish as well. Mine had two full rows of dots on each side.
I have been interested in trying JD's though. You'll like the CK though.