It fit the tank more or less, kinda. But when it got mad, it would park in the middle of the tank and no fish could get by it. He would dig a tremendous hole under a stump in the middle of the tank, get in his hole, and all the fish were one end of the tank or the other. And they get bigger than 10 inches, too--and fast. They need some room. I was growing out the Lyonsi with a Zonatus, a Syn, a Breidohri. The Lyonsi outgrew 'em all before I could get a bigger tank and he started getting crazy. He eventually slammed his head on the lid and died. He was a piece of work.
And they're not nice peaceful fish, either. I've heard that Lyonsi are a peaceful version of a Trimac, but that ain't sayin much.