  We describe a new class of BPS objects called magnetubes: their supersymmetry
is determined by their magnetic charges, while their electric charges can
oscillate freely between different species. We show how to incorporate these
objects into microstate geometries and create BPS solutions in which the charge
densities rotate through different U(1) species as one moves around a circle
within the microstate geometry. Our solutions have the same "time-like"
supersymmetry as five-dimensional, three-charge black holes but, in various
parts of the solution, the supersymmetry takes the "null" form that is normally
associated with magnetic charges. It is this property that enables the species
oscillation of magnetubes to be compatible with supersymmetry. We give an
example in which the species oscillate non-trivially around a circle within a
microstate geometry, and yet the energy-momentum tensor and metric are
completely independent of this circle: only the amplitude of the oscillation
influences the metric.
