A fluid reaction tank is provided having an inlet vortex tube for receiving fluid having suspended solids therein and to impart a vortex motion on the fluid flowing therethrough into a reactor housing having one or more cartridges containing a flocculant composition. The cartridges can have perforated inner sidewalls to allow contact of fluid with the composition. The cartridges can further have vortex forming ridges therein to impart or to maintain the vortex motion of the fluid flowing through the fluid reaction tank.