I got it from a seller
http://www.amazontropicalfishllc.com/ already at about 1.5'. He grew little and slow in the year or so that I had him due to feeding probems etc. as you read or perhaps it is their nature - my miniscule experience is not enough.
Yeah, I remember vaguely about Michael's leerii killing a big arapaima too, you are right.
Again, you can see this over and over again about Wallagoes, other "highly aggressive" fish - Hemibagrus like ARTC, wyckii, etc.: it's a risk and risk, by definition, is that the (un)desirable outcome may or may not occur as so much is dependent on the ever so greatly varying circumstances, tank set up, size, tank mates, sizes/ages, sexes, tank dynamics, feeding, etc. etc. etc.
BTW, here is Michael's input on the death of his 3' yarelli, in case you have not seen it:
http://www.planetcatfish.com/forum/viewtopic.php?f=9&t=31656&hilit=+leerii