In the present study, biosorption and bioaccumulation characteristics of Riccia fluitans to be use as biological mineral feed supplement, was investigated. Preliminary studies showed that R. fluitans was rich in protein (27-31%) and possessed high cation exchange capacity (14.5 mequiv g(-1)) and therefore it has the potential to find an application as biological carrier of microelements that are supplied to feed of animals, the diet of which is deficient in these components. In the present study, various processes of enrichment with microelements of crystalwort were investigated, including biosorption, bioaccumulation by non-growing and growing cells in single-(Cr(III) ions) and multi-metal system (Cr(III), Cu(II), Mn(II), Zn(II) ions). The effect of process parameters (temperature and pH) on metal ions binding efficiency was studied in single-metal system. It was found that at 20 degrees C and pH 5 the biomass bound 106 mg g(-1) Cr(III) ions. The experimental results showed that the mostly advantageous process of metal ions binding was biosorption, the process that is also the mostly cost-effective. (C) 2006 Elsevier Ltd. All rights reserved.