Its not the flavor of the pellets, its the hardness of the pellets. If you want to discontinue using flakes, then you just have to stop feeding flakes. It will likely take a month or more, but ultimately it will eat pellets if that's all that's offered. Don't worry, a healthy fish can go for months without food. Its the same as training a fish off live food and onto pellets. You can help the process along by pre-soaking the pellets before feeding to soften it up.
Yeah, it seems like i will need to take this route. I bought the fish online and came in horrible shape. Ill feed it flakes and mix in soaked pellets for a few more weeks and get it healthy and then feed nothing but pellets until it eats them. Thanks!