It has been reported that species such as common carp are unable to utilize exclusively FAA or peptide-based diets (Zhang, Dabrowski, Hliwa & Gomułka 2006) in comparison with stomach-possessing fish such as rainbow trout. In the latter species, synthetic dipeptide-based diets have sustained high growth rates (Terjesen, Lee, Zhang, Faila & Dabrowski 2006). Therefore, it is worth determining whether experimental, protein-, peptide- and free amino acid-based diets are adequate for larval stomachless fish, whether commercial and purified diets are comparable as the first/exclusive feed for growth and survival and to examine whether FAA concentrations in the fish body are potential indicators of the availability of amino acid sources.