The objective of the present study was to investigate the behavior of CaCO3, crystal formation at the very beginning stage of fouling. This article describes an experimental method which employs a light microscope system to visualize crystal growth behavior during the fouling process inside a transparent rectangular channel. Crystal visualization data are presented to examine the crystal growth behavior of calcium carbonate crystallizing from hard-water fouling. The present study provides crystal growth data as a function of time, which includes crystal creation, crystal growth, the number of crystals, and removal process. Both the rate and location of crystal growth were found to be dictated by small seed crystals formed in the early stage of fouling. The removal rate was found to be almost negligible compared to the deposition rate.