In a new study of viral abundance over a short time frame in the Sargasso Sea, researchers found that almost all viruses with cyclical changes in abundance were most active at night – somewhat surprising when the team expected microbial behavior to pick up pace when light was available for photosynthesis. It turns out the viruses most busy at night were not infecting bacteria that perform photosynthesis, which are among the types of bacteria known to be infected by viruses. Instead, these overnight viral hosts were microbes that focus on consumption of other organic matter because they can’t produce their own food. The findings reveal another level of complexity of viral interactions with marine bacteria, opening the door to new questions about how these dances in the dark influence ecological services provided by the world’s oceans.