Shrimp should be shipped with a heat pack in a styrofoam box this time of year. Anyway, floating the bag in the tank as I suggested will equalize the water temperature inside the bag to that of the tank over the 20 minutes, especially when tank water is being added to the bag. I've never acclimated my shirmp (RCS, yellows, snowballs, CRS) to any extent other than using the process I mentioned earlier and they were all fine. Caridina sp. are a little more finicky than the Neocaridina sp. and probably wouldn't survuve the trip if the temps in the bag dropped to the 50's, whereas the Neocaridinas can live in near freezing water but they will stop breeding in about the 50's.