Small aquarium fishes (e.g. zebrafish and medaka) are easily available and maintained, and therefore are most appropriate for high-throughput and large-scale toxicity screening of chemical compounds, including water contaminants. They allow the toxic effect to be assessed earlier, faster, and at a lower cost. The highly conserved developmental processes and toxicological responses between zebrafish/medaka and mammals, allow for human health-risk inference in the case of environmental exposure. The amenability of the zebrafish and medaka fish to various molecular tools and availability of many transgenic lines and vast genomic resources make them highly versatile models for mechanistic, comparative, and predictive toxicological studies. The goal of this project is to use small aquarium fish coupled with molecular-biochemical approaches for monitoring contaminants of emerging concern (CEC) in water.