Fluidized bed apparatus for use in applying a coating, having a relatively lesser density, to particles, having relatively greater densities by causing passage of a gaseous atmosphere through a bed of the particles. The apparatus includes an enclosure holding a bed of the particles and means for causing flowing of the gaseous atmosphere carrying a material for forming the coating through the bed of particles to be fluidized. The apparatus further includes means for adding seed particles to the bed and weir tube means removing coated particles from the bed when the contents of the bed achieves a predetermined level. Finally, the apparatus includes discharge means receiving the coated particles from the tube means and conveying them to a collection location remote from the enclosure.