This work deals with the design and application of a neuro-fuzzy controller of the magma density of the fine crystals for the stabilisation of the crystal size distribution (CSD) of the product from an MSMPR (Mixed Suspension, Mixed Product Removal) continuous crystallizer. The cooling crystallization of potassium sulphate from aqueous solutions in a pilot-scale stirred vessel was investigated. A control strategy, based on the elimination of fines by using a combined sedimentation-dissolution device, is presented. The control scheme was successfully applied to a pilot-scale draft-tube (DT) crystallizer and yielded promising results. The proposed process control system allowed the reduction of the fines fraction by more than 30%, while maintaining operation stability and short transient responses.