The magenta color is leftover sensitizing dye.(posted 9102 days ago)You do _not_ need to fix the film forever to remove it; it will, however, need a minute or two longer fix time than standard films.
To remove the dye, use a wash aid. You can buy the prepackaged stuff or make your own by dissolving a tablespoon (about 25g) sodium sulfite in a quart of water. After fixing, treat the film in the wash aid for two to three minutes with constant agitation, then wash and dry normally.