they are extremely picky. some say that they have been able to get mandarins to eat prepared foods, but i think the odds are about 40 to 1. in other words, i have heard of 40 folks who failed to 1 that succeeded.
there is a company called ORA, that only sells to stores. they claim they have mandarins that eat prepared foods. they are much more expensive than the wild caught ones, but if it's true, it's well worth it. i would inquire at your local pet store to see if they order from ORA at all, and what the availability is on one of their fish.
sea apple? how long have you had that?