Perfusion processes are rapidly being adopted as an alternative to traditional batch and fed batch culturing of mammalian cells. In one type of perfusion system, a bioreactor is connected to a recirculation pathway where the exchange of spent media occurs. Rocker bioreactors, also commonly referred to as wave bioreactors, have been a popular choice for seed train applications and small scale protein production for required working volumes below the 100 L range. The continuous rocking motion of the reactor generates a wave inside of a single-use biocontainer, allowing aeration of the cell culture while avoiding problematic high shear conditions. However, one commonly encountered challenge of using rocker bioreactors in perfusion mode is the undesirable transfer of air into the recirculation pathway. These entrapped air bubbles compromise the effectiveness of the perfusion filter, which is usually accomplished via either a tangential flow filtration (TFF) or an alternating tangential flow filtration (ATF) device. This technical bulletin evaluates a solution to enable perfusion culture via a new anchored dip tube that was designed to prevent air migration into the recirculation pathway. A 50 L FlexGro® biocontainer connected to a recirculation loop was tested for the presence of entrapped air under varying processing conditions of liquid volume, rocking rate, and rocking angle. The experimental data provides insights into the relationship between liquid volume, rocking rate, and rocking angle, which is useful in defining the proven acceptable range (PAR) of processing parameters for the perfusion system.