Microbubble generators are of considerable importance to a range of scientific fields from use in aquaculture, engineering to medical applications. For aquaculture, in particular, microbubble generators are used in farms where high water oxygenation is necessary to ensure farmers maximize the amount of seafood that they produce. This is due to the fact the amount of sea life in the water is proportional to the amount of oxygen in it. In this paper, experimental measurements and CFD simulation are used for geometrical optimization of the Venturi-type microbubble generator. Using the experimental results to validate the model, further research has been completed specifically investigating the effect of the change in throat length to throat diameter ratio and the effect of the diffuser divergent angle on the bubble diameter at the exit section. The experimental results showed that increasing water flow rate and reducing the air flow rate produces smaller microbubble diameter. The prediction from the CFD results indicated that throat length/throat diameter ratio and diffuser divergent angle have a small effect on bubble diameter distribution and average bubble diameter for the range of the throat water velocities used in this study.