I've had three of these frogs at one time, and I couldn't tell who was who until they were bigger in size. Once they reach full size, it is very easy to tell. Until then, it's anyone's guess. If yours is malnourished, it might be even harder. I would feed it every day until it plumps up and grows a size or two. Then I would put it on a regular feeding schedule. Mine loved to eat bloodworms, guppies, feeder fish, crickets, brine shrimp and pretty much anything they could fit in their mouths. Feeding time was always a joy to watch. I agree with John on the Melafix. These frogs are tough and can handle pretty much any conditions, but I would not use Melafix with them at all. It puts a coating on the skin, and all frogs need their skin free of any substance in order to properly moisturize and breath. Definitely not a good idea. These frogs make great pets-I hope yours gets healthy soon and you enjoy many years with him/her!