There are several methods available for the enumeration of microalgal cells. However, due to the small size of the microalgal cells, most methods are not very accurate. In addition, some of the methods described here require sophisticated and expensive equipment, which is beyond the reach of some research laboratories. The choice of counting device depends on culture density, the size and shape of the cells or colonies being counted, and the presence and amount of extracellular threads, sheaths, or dissolved mucilage, which can influence the filling of the counting cham­ber (Guillard and Sieracki, 2005). Moreover, the method to be adopted for a par­ticular sample will therefore depend on other factors such as detection range, costs, sample throughput, health and safety considerations, inter alia.