Looks like it is settling right in. I think you have a healthy haddoni there. Once they settle in and start feeding, they are actually considered quite hardy. It's the transit and settling in that is sometimes touch-and-go. In a few days to a week, you could begin to feed it small pieces of fresh from the supermarket shrimp, squid, or silversides. As you have heard I'm sure, haddoni like to eat. This sometimes includes other fish/inverts in the tank.