In this study, the fungal communities of wood and mixed-diet fed P. nigrolineatus GI tracts were investigated via rDNA ITS sequencing. Due to complications associated with fish acquisition and rearing, we were only able to analyse one fish raised on each diet. While we recognise that a rigorous analysis of the GI tract communities requires the utilisation of several fish, we found that each GI tract region possessed a distinct fungal community and this is the first report of the presence of fungi throughout a fish GI tract.