It will need to be in the other tank for a few weeks minimum, I generally run media for at least two months before moving it to a new tank. You’ll need to rely on “bacteria in a bottle” like Dr. Tim’s. I used Microbacter years ago, I don’t recall that the results were all that stellar, but maybe my memory is faulty.
The microbacter op is using is xlm which is only a few years old. Not sure if its different bacteria than microbacter7 or if its just much more concentrated.