In this work, we study the fibre flocculation response created by a dual component retention system subject to different addition and mixing conditions. The motivation for this work is to develop new approaches to optimize the performance of retention aids systems for improving the retention-formation relationship. We do so through a combination of pilot scale production trials in combination with semi-pilot scale flow visualization using a cationic Polyacrylamide (CPAM) polymer and silica micro-particle retention system. Specifically, we investigate the effects of local turbulence levels, hydrodynamic shear applied to the polymer phase, and the time between addition of the polymer, micro-particle and to the headbox/forming section. Results from our production trials showed that optimal retention system performance can be achieved when the polymer and micro-particle components are added only a fraction of a second from each other and from the headbox in the presence of high levels of turbulence and with exposure to minimum hydrodynamic shear. Under optimal conditions, the improvements in retention realized were over 50% with simultaneous improvements in formation in excess of 30% with respect to a reference case. We then attempt to understand the mechanisms for this optimal response by simulating the same addition and mixing conditions on an experimental flow loop. The suspension flocculation dynamics are studied by visualization in a transparent pipe section. It is shown that when the polymer is exposed to high shear, the suspension does not reflocculate, even after addition of the micro-particle, which correlated with low filler retention in the production trials. When turbulence levels remained low, the suspension flocculated very quickly upon addition of the components, reaching large floc sizes in a very short amount of time. This correlated to poor formation in the production trials. When the retention system components were added immediately downstream a turbulence source but not subjected to any additional shear, the fibre floc size remained small and showed a slow tendency toward reflocculation. These conditions correlated to optimal retention and formation in the production trials.