They sometimes eat humans or little fury gerbils(mouses) so stay away

I've kept Black Racers(Coluber constrictor) snakes, and the related Coachwhips, for many years. Black Racers DO NOT eat fish, or any invertebrate animals, and will not even recognize those as food sources. They DO eat small rodents, primarily mice, but will also eat lizards and occasionally, smaller snakes. They will also eat small birds or bird eggs. In captivity most will eat mice. Hatchling Racers will eat small lizards or "pinkie"(newborn)mice.

Bugs

Black racer snakes are an important link in the food chain in the natural ecosystems of the world. The typical prey of the black racer snake depends on the size of the black racer snake. It usually includes small varieties of invertebrates, such as slugs, worms and insects. They also eat fish, some varieties of amphibians, other snakes, birds, the eggs which are laid by birds, and some species of small mammals.

Some species, including the black racer snake, the black rat snake and the milk snake also consume a large number of rodents. They can be seen around barns and it is because of the fact that they eat rodents and other farm pests that they are of great help to farmers. They frequently enter the burrows of mice and rats and eat their young, and they also like slugs and other species of insects that have soft bodies.

Black Racers eat slugs,fish,other snakes,species,worms,and insects.

They eat slugs.fish,other snakes,and even small soft mammals.

Mostly small rodents