A semi-continuous flow reactor was used to mimic gel supersaturation conditions at both intermediate and terminal stages of zeolite batch synthesis. Flow of nutrient into the reactor was repeatedly switched on and off. Analysis of the crystals by atomic force microscopy (AFM) reveals that samples removed under simulated conditions of gel depletion are topographically similar to samples prepared by normal batch synthesis, with very low levels of surface nucleation. Samples removed under conditions of high gel supersaturation appear to be growing by the same mechanism however rates of surface nucleation are increased by up to two orders of magnitude. Crystal growth resumes uperturbed upon reconnection of the nutrient feed. Ability to exert control over surface nucleation rates has important ramifications for the potential control of defect inclusion.