  In this paper we consider an Euler fluid coupled to external
electromagnetism. We prove that the Hopfion fluid-electromagnetic knot,
carrying fluid and electromagnetic (EM) helicities, solves the fluid dynamical
equations as well as the Abanov Wiegmann (AW) equations for helicities, which
are inspired by the axial-current anomaly of a Dirac fermion. We also find a
nontrivial knot solution with truly interacting fluid and electromagnetic
fields. The key ingredients of these phenomena are the EM and fluid helicities.
An EM dual system, with a magnetically charged fluid, is proposed and the
analogs of the AW equations are written down. We consider a fluid coupled to a
nonlinear generalizations for electromagnetism. The Hopfions are shown to be
solutions of the generalized equations. We write down the formalism of fluids
in 2+1 dimensions, and we dimensionally reduce the 3+1 dimensional solutions.
We determine the EM knotted solutions, from which we derive the fluid knots, by
applying special conformal transformations with imaginary parameters on
un-knotted null constant EM fields.
