Graduation date: 2006An acceptable microparticulate diet for marine fish larvae may be defined as an artificial diet that contains, retains, and delivers the required nutrients to support survival and growth. Factors affecting ingestion rate of prey items by fish larvae include environmental factors such as light intensity, prey/background contrast, possible chemical cues, and co-feeding with live foods. The efficient addition of FAA (free amino acids) in microparticles, at concentrations similar to those found in live foods may reduce or eliminate the need for exogenous proteases and FAA from live feeds. Complex particles (CP), when coupled with optimization of environmental parameters, may result in ingestion of artificial diets at rates sufficient to support high survival and growth rates. Lipid spray beads (LSB) have shown promise in their ability to deliver low molecular weight water-soluble (LMWS) nutrients to marine fish larvae. Furthermore, ingestion and digestion of zein-bound complex particles (CP), with incorporated LSB, by fish larvae have been reported. Here we describe improvements in LSB technology as well as feeding conditions for the effective delivery of FAA to blue spotted goby larvae (Asterropteryx semipunctata). The FAA glycine was used as a model LMWS nutrient due to its high solubility in water. LSB performance was found to be optimized with an aqueous core concentration of 400 g l-1 glycine and was shown to have significantly higher DE over a 60 min period in aqueous suspension compared to that of beads with lower core glycine concentrations (two-way ANOVA; p<0.0001). Evaluation of core to lipid ratios (v/v) showed that retention and delivery efficiencies of LSB containing cores of 400 g glycine l-l at a core to lipid ratio of 1:2 v/v were greater than those of LSB with other core to lipid ratios. The use of optimized LSB in zein-bound CP resulted in an encapsulation efficiency of 4% w/w glycine for the CP, which was within the range of FAA concentrations reported for rotifers, Artemia and copepods. Blue spotted goby larvae showed peak feeding incidence at a light intensity of 5.44 µE s-1 m-2 when fed on CP against a black background. Higher or lower light intensities and a white background, were shown to independently reduce feeding incidence. In a 5 day feeding trial, larvae fed CP containing LSB with core material consisting of casein, hydrolyzed casein, or a mix of FAA (based on the average of the amino acids found in casein and hydrolyzed casein) showed 6, 8, and 6% survival respectively, which was significantly lower than 37% survival for larvae fed the marine phytoplankton, Tahitian Isochrysis galbana and Rhodomonas sp. (p>0.05). At 0% survival, the starved control had significantly lower survival than that of all other treatments (p<0.05).