The influence of liquid shear rates on the development of acidifying mixed-culture aggregates was studied in a gas-lift reactor. The glucose concentration was kept at a constant and relatively high level by operating the reactor in pH-auxostat mode. Size, strength, and wet density of aggregates cultivated at different superficial gas velocities (U-g) were investigated. Image analysis showed that the Sauter mean diameter (D-s) decreased with increasing U-g. A stirred tank was used to characterize the surface detachment rate (R-d) under non-growth conditions. An exponential decrease was observed in R-d with the applied U-g during cultivation, i.e., aggregates became stronger. The increased strength coincided with an increase in aggregate wet density. Size classified aggregates showed an increase in R-d with the square of the aggregate diameter (D-p), however, this contribution was much smaller than the effect of adaptation. Experiments in a similar gas-lift reactor under dynamic conditions without adaptation, showed that R-d increased exponentially with increasing U-g. So, two important contributions to R-d can be distinguished: adaptation, which induces stronger aggregates, and aggregate size, which makes them less susceptible to hydrodynamic shear. A general expression for R-d was derived, which depends on D-p and U-g. Combining this equation with the surface biomass growth rate (R-g) allowed for the estimation of the maximal diameter (D-max) aggregates can reach at any U-g, and it was found that the estimated and measured D-max,, were in good agreement.