Location of sampling is decided by the purpose of the study. The habitat, food preference and so on of the organisms will influence greatly the selection of sampling stations.
When the sample is brought into the laboratory, it is often necessary to concentrate the organisms in a relatively small volume of water. For this purpose, the water may partly be filtered rapidly through a fine milling cloth and the residure quickly poured back into a suitable container before filtration is completed.
Biofilm scoured from media put in a container, and then a small volume of water is poured on it. The sample is collected, and a ample air space is left in the bottle (at least 1/2 volume) to supply oxygen. The container should be kept at about 10 degrees C.
Pipet free-living organisms under a binocular dissecting microscope (magnification: x10 ~ x20) , and begin separate cultures.