I just pour some rubbing alcohol on a small baggy about half full of leftover minnows. No need to totally submerge them, just enough to get them in the alcohol to preserve rhem. Due to the alcihol, they don't freeze. They thaw out in a few minutes and stay fairly firm from the alcohol, where just plain frozen minnows turn to mush after thawing. I have found much less discoloration with the alcohol and the firmness makes a big difference.