They can be without light for awhile. People ship coral with no light and the coral is almost always alive, you get the idea? They will be fine with just water circulation for awhile. I doubt you will need to run a ca
reactor when transferring. Use as much of the old water you can. Don't use bacteria in a bottle, waist of money IMO
and your live rock and sand from the 125g harness all the bacteria you will need. I think you could easily get away with adding 50-80lbs. more live rock. I would do a 25% water change the next day (just what I would do). Add 1. live rock, 2. coral, and 3. fish. I would put them on the top back left and right corners and point the towards the surface aiming at the center so you get a V kind of flow.