I need one, and the Feebas don't want to evolve >_> I think that and maybe one other Pokemon is needed to be evolved or something before I can upload it to Diamond.
To evolve Feebas, feed it the VERY BEST Poffins that increase Beauty. It needs to get to at leas 170/255 Sheen I think. Then, level it up. If the Feebas is full, there is no way to gain more Beauty and you'll need another Feebas. Make ure that the Feebas ISN'T:
-Adamant
-Impish
-Careful
-Jolly
These natures above hinder the Beauty stat, along with your Feebas not liking them.