Excessive curvature of the back, and it doesn't appear to be the photo angle.
Post a poll at MFK where you have also posted, to see what size is best. Ignore the folks who just want the big fish cause its cool and listen to the serious aquarists. In fact, just do a search on the many past posts over the issue.
You can google the species and learn all you want, or care to.
The charging/flaring is from natural behavior since they think you are invading their territory, obviously a larger area than you are providing.
A 55/75 gal might have been adequate for growout to 8-10", but not for long term, especially where you can achieve 18-22". This is all my opinion, you will end up doing what you want, I just think a 75 gal tank is too small for a 14" fish (Jag).