Yeah, just jerking your chain a little. The thing is: Even if you buy a 2 incher and feed it perfectly, keep it at optimum conditions and love it like a fat man loves cake, there's no guarantee you'll get the maximum listed size fahaka. Just like people, genetics plays into the total growth potential of fahaka and any other fish or animal. Getting a fahaka to 18", while a worthy goal, can't be a defining decision on what fish to get. My advise would be, if you see one for sale that's close enough to you or shippable at a price that seems reasonable and it seems to be healthy and parasite free, go ahead and grab it. If it gets to be 18", you'll be ahead of the game and if not, you've at least got the fish you want.
NOTE: While 18" is listed as the max size, I've NEVER heard of anybody on ANY forums I go to that have one that large. The largest I've ever seen reliably measured was about 16". Not saying they don't exist but in the 20 years, I've been in the hobby and the 10 years I've been cruising the internet, I've never seen it.