Abstract: An apparatus for magnetically treating fluid in a fluid conduit includes one or more magnets adapted for placement adjacent a fluid conduit in such a manner as to allow the magnet(s) to subject fluid flowing within the conduit to magnetic field(s) produced by the magnet(s). The magnets are enclosed by inner and outer shields of, respectively, non-ferrous and ferrous composition. In some embodiments apparatus according to the invention further comprise coils having pluralities of contiguous non-overlapping turns axially enclosing the magnet(s) and the fluid conduits adjacent to which the magnet(s) are disposed. Apparatus according to the invention may advantageously be employed in pluralities connected in series and/or parallel relationships.