My first one also withered and died, but it arrived with a sunken belly and was painfully thin to start with, I half expected it to die as soon as I saw it.
Now have another one, arrived much fatter, about the same length 3-4" didnt eat for maybe a week or so, then I fed it some feeders, neons if I remember right, then slowly moved to bloodworm, and now he eats literaly anything.
BUT, they really arent very good at finding food, it literaly has to touch/hit its whiskers for it to eat whatever it is, it wont actively search for food.
What I do is drop food so the current makes it pass him, or what I used to do was use a REALLY long pair of tweezers and touch his whisker with the food to promote a "strike" .
Hope some of this was of some help
