Hmm, good question...
Since the fish are biting sooooo slow these days due to cold water, I wonder if minnows would stay active enough to draw bites.
They might die before anything goes for them.
From what I have read about cold water fishing, most predator fish are hanging out and barely moving next to cover, any kind of cover, and the sun seems to be warming up some spots as the sun heats the day.
Bobber or not, near the surface or near the bottoms, fish slowly by cover and try to determine depth of cover after a few casts.