They are natural herbivores so it should be fine, but how long have you had the tang and what have you tried feeling it? There are so many choices in food that I'm sure you can find something it likes i.e Marine Cuisine, Emerald Entree, Mysis, Brine, Squid, Mussels, Clams on the half shell and try mixing Garlic in with the food to entice it to eat...good luck.