Qualitative and Quantitative Bacteriological Studies on a Fluidized Sand Biofilter Used in a Semiclosed Trout Culture System.

Abstract : We conducted a study of the numbers and types of heterotrophic bacteria that occur in a fluidized sand biofilter and in rearing water in a semiclosed trout culture research system at the Freshwater Institute, Shepherdstown, West Virginia. Methods were developed for sampling the biofilter at various depths, removal of bacteria from the biofilm on sand particles, selection of appropriate media for enumeration of bacteria, and plate count procedures. Sonication of sand from biofilters and a spread plate technique provided the best results in determining total counts of heterotrophic bacteria. In addition to determining total heterotrophic bacteria, the study was designed to detect the presence of the opportunistic fish pathogens Aeromonas hydrophila and Pseudomonas fluorescens, as well as denitrifying bacteria.