am I correct in thinking your current tank is only just cycled?
you need to give the bacteria colony a good chance to settle and get established before removing a chunk of the media so make sure you give it a month or so.
depending on the size of the new tank in relation to the old one you can either move across some of the media and stock straight away, or move across some of the media then fishless cycle which shouldn't take long with the mature media already in