I had a brasiliensis that I grew out from about an inch, and he was so placid.
He shared his tank with a bgk and silver dollars and never hurt anyone. He never bothered the knife and only chased the dollars to show off but never actually hurt them. I even had some black widow tetras in with him temporarily, and he never bothered them even though he could of swallowed them whole.
However, apparently they're not all nice, and can be total jerks, and I've been told this is the more likely scenario - you have been warned!
Here's a pic of Horrace at around four years old (12"ish, he grew another inch or so before we lost him)
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If I ever got another one however, personally I couldn't keep it in anything less than 2' wide, but most would disagree so I thought I'd put it out there (plus it gives me a chance to show off my Horrace

)