I went back and looked at the date on the first time I posted his picture it was january of this year. He's about 8". His diet is high protein. Mostly fresh raw shrimp and scallops supplemented with pellet, worms, and grubs. I use a color enhancing supplement that I purchased from Jehmco.
I think the growth rate varies greatly with the size of the tank, water changes and diet. And in particular after seeing this guy against his siblings (heretofore called "lunch") I would say the individual fish. I have nine other Managuense right now and have had many over the years. This one is the nicest when it comes to pattern and color.
I've only ever been bitten twice. Once by a Blood Parrot and one other time by a Citrinellum. Never had any problem putting my hand in a tank with any of the fish...up to and including the Wolf Fish. I read in an article that when you take a photo of the fish the barrel of the lens looks like an open mouth coming toward them. I'm sure that's part of it.