Colony Forming Units. This is a measure that indicates the number of microorganisms in water.The colony forming units usually make up of bacteria and are of the same organisms that grow together. Other forms of colonies such as those made up of filaments produce moulds as they develop simultaneously. CFU units can be considered depending on the kind of sample being tested such as per unit area, per unit volume, or per unit weight. In order to ascertain the amount of CFU units, samples are done and distributed throughout the surface of an agar plate and then nurtured at an appropriate temperature for a period of time. As the colonies build up they are counted, but made sure not to be counted as individual cells since a colony can be formed from a single or a large number of cells.