Loeffler's medium is-

Enriched media The media containing ingredients which enhance their growth-promoting qualities E.g. Blood agar, Chocolate agar and Loeffler medium. The usual media employed for cultivation of the diphtheria bacillus are Loeffler's serum slope and tellurite blood agar. Diphtheria bacilli grow on Loeffler's serum slope very rapidly and colonies can be seen in 6-8 hours, long before the other bacteria grow. Best Selective media for Corynebaterium is Potassium tellurite agar.