The oceans of the world are extremely important for life on earth. Every day, they produce a large amount of oxygen needed for breathing and, at the same time, they absorb carbon dioxide produced by humans. If we did not have the oceans, this carbon dioxide would build up in the atmosphere much faster than it is accumulating now, leading to faster warming of the earth. In the ocean’s sunlit surface, the carbon dioxide is absorbed by small living cells called phytoplankton. Some phytoplankton are consumed by larger organisms and are transferred to the deep ocean. In this article, we investigate the effects of small, fast-swimming fish that feed at the surface during the night and stay in deep waters during the day. In doing this, these fish move carbon from the surface to feed the bacteria living in deep waters.