Fluid treatment apparatus having an alloy disk assembly comprised of a plurality of disks, each prepared from the metal elements copper, zinc, nickel, silver, and tin, which individually exhibit great propensity for reducing scale formation in flow conduits; particularly when combined together to form the fluid treatment alloy disk assembly of this disclosure. The disk assembly is housed within a suitable enclosure having passageways arranged to effect countercurrent flow through a series of apertured disks. The close proximity of the counterflowing streams within the alloy disk assembly provide unexpected advances in the art of fluid treatment.