as a baitfish in the US (Stone et al., 2005), and it is widely used as a toxicological and biomedical model in research (Ankley and Villeneuve, 2006). Although a variety of live and prepared diets are used to maintain this species for research and commercial purposes, the nutrient requirements of fathead minnow are virtually unknown. Like other cyprinids, these “stomachless” fish do not secrete hydrochloric acid during digestion, which might alter the availability of nutrients from the diet. In particular, mineral availability could be lower in agastric species than in those with true stomachs because mineral absorption is enhanced at a low pH (Davis and Gatlin, 1996).