If you want to change the media what is reason behind that?
If any suitable reason is there you can validate new media which you want to validate with respect to old one.
Three consecutive days for three lot.
You have to perform GPT with both the media, check the counts, Growth pattern, identification of culture from both the media, validate the incubation time.
This all you have to consider and after completion of validation for testing you have to run three batch with both the media.
After completion of all this study you have to repalce your media without as per regulatory point of view.
For furture clarification please fill free to contact me on : firstname.lastname@example.org.
Thanks and Regards,