This study describes experiments carried out in a fluidized bed reactor (FBR) to observe the active mechanisms occurring during the precipitation of nickel hydroxy-carbonate. The fluidized bed process presented in this paper is suitable for recovery of metal ions from solutions in the form of solid coated onto a silica sand surface. The solution containing the metal ion was pumped vertically upwards into the bed and the precipitating agent was injected horizontally into the bed. The solid material was deposited on the surface of the fluidized silica sand. During the process, particle enlargement takes place by heterogeneous nucleation and/or aggregation. In this work a new approach is presented which is able to control the supersaturation levels in the FBR by multiplying the feed points (FP). The particular focus is to describe the relationship between fines, metal removal in the reactor system and chemical performance of the FBR. The influence of change in the number of feeding points in the process was investigated by monitoring fines produced during the process by particle size distribution (PSD), atomic absorption spectroscopy (AAS) and scanning electron microscopy (SEM). The concentration of fines was found to correlate with the degree of supersaturation, and excess fines production was reduced by increasing the number of feed points. (c) 2005 Elsevier Ltd. All rights reserved.