Great looking Planiceps Sharptooth! Definitely makes me miss mine. When I have the time to grow one out again I will have the means for a massive permanent setup. I've grown them from 2" to 30" in the past in less than a year and a half and would agree that they definitely don't need Nekton to survive. I noticed my Planiceps to never be nearly as aggressive as a TSN when it came to eating and generally to have a mentality more along the lines of a Tigrinus. They are definitely similar to Tig's when it comes to water quality needs as well, excellent oxygen and high current flow.
Where did you pick it up from?
His are over 4ft I know for sure. I think one was 52" last time it was measured if my memory serves me right and that was like 6+ years ago. They are beast!