It depends upon what you are trying to accomplish. If you just have a few birds for "pretty", you can feed scratch, wild bird seed, poultry or game bird pellets. If you are raising birds for flying competitions or show, you would want to use some of the specialty pigeon feeds. If you don't have a book on pigeon raising, try getting one or borrowing one from the library. Also you might do a computer search for pigeon feeds. The variety of pigeon feeds covers a wide spectrum.
Fantails are great birds! I have a whole loft of them. They are funny little birds. Fantails are very bad flyers, so they become lunch very easy. I only let mine out of the loft , if I can watch them. Good luck you will enjoy them.