Ya the clown knife will definatly get too big. I had one that was 24" and he got that large in a little over a year. And the guy I bought him from kept in a 55G(cruel as he was twice as long as the tank was deep, not a lotta room.
needlefish are not gars!!!!!!!! there latin name is xenentodon cancila. they grow to about 12". but they will be very difficult to wean onto dead foods.