We propose a model of competition of n species in a chemostat, with constant input of
some species. We mainly emphasize the case that can lead to coexistence in the chemostat
in a non-trivial way, i.e., where the n−1 less competitive species are in the input. We prove
that if the inputs satisfy a constraint, the coexistence between the species is obtained in the
form of a globally asymptotically stable (GAS) positive equilibrium, while a GAS equilibrium
without the dominant species is achieved if the constraint is not satisfied. This work is
round up with a thorough study of all the situations that can arise when having an arbitrary
number of species in the chemostat inputs; this always results in a GAS equilibrium that
either does or does not encompass one of the species that is not present in the input