Understand that starving a fish like this takes more than a few days. Ive starved some large predatory fish for a month to get them to eat, and they didnt even show sign of slimming down, so they can have alot in them. I never was able to train my CK toeat floating food. Make sure you feed it at night with the lights off coz thats when its most comfortable to feed. Anyway be careful when starving a fish coz its not nice. I only did it coz they wouldnt eat anything at all when I first got em (two barramundi) so I had no choice but to keep throwing food at them until they took it. It also helps to have a quarantine tank where you can keep the fish by itself so no other fish interfere with its feeding, but thats not really worth it if you just want to get it to eat some leftover food is it?