I have only had my iridescent shark for a week now, he is 12.3 inches long and has a decent girth. I got him from a local pet shop that had him in a 150g tank with a handful of other very large and aggressive fish so he has some battle wounds and they are working on healing. I've got him in a 200 g tank with 2 tinfoil barbs and I do not see him eating. I realize that one of the characteristics of this fish is the constant swimming back and forth in the tank, and for the most part, he is swimming normally, not frantic or like he is in a stressed-out panic. I have him in a corner that doesn't see much action or movement, and I can come up to the tank and he will come to me right to the glass. What worries me is that I haven't seen him eat and then his panic swimming from time to time. the water quality is good I monitor it daily and while I am not an expert aquarist, I am not wet behind the ears either. not only do I dig this fish a lot but I spent decent money on him and I am not trying to lose him. I have tried every conceivable type of food from live to pellet and I have yet to see him eat, though I know that doesn't mean he isn't easting when I'm not looking lol.