I have had a Valentini for at least a year now. He's ~2.5" (hasn't grown much since I got him), and gets along just fine with everyone else in my tank, fish, shrimp, crabs and snails. He might be an exception, because puffers are usually aggressive. He eats flake, frozen prime reef and tetra tabs. I see him snooping around my seaweed, but don't know if he actually eats it. He freaks out my tank-sitters because when the lights are out, he will wedge himself into a corner and "go to sleep" - they thought he was dead the first time they saw it
He's a great fish IMHO