had gravel as a hydroponic support medium which served as a Ca source, whereas we used NaHCO3 to maintain alkalinity. Also, the mineral composition of the diets were probably different in the two studies. Rakocy et al. (1993)reported that the relative accumulation rates were K>N>P>Ca>S>Mg when KOH was added as an alkalinity source and that the micronutrients Fe, Zn, Mn, Cu, and B did not accumulate with respect to cumulative feed. In this study, changes in the dissolved quantity of micronutrients varied significantly with treatment level for Zn and Mn, but not for Fe and Cu.