Ciliophora are one of the biggest and oldest known Phyla of protozoans. Most ciliophora are free living, but some are commercial or parasitic, these small creatures are distributed all over of the world and can be observing in all fresh and marine waters on the earth. The ciliates are characterized by numerous cilia on the cell surface and possessing two kinds of nucleus, that is; macronucleus and micronucleus. In the present study we consider the diurnal fluctuations of ciliophora. The sampling was done in summer 2014, from a fixed point, 15 centimeter below the water surface at an interval of 6 h on the 10 of each month, from Hindudar Lake. The samples were subjected to some physico-chemical parameters (atmospheric and water temperature, dissolved oxygen, pH and total solid) and free living ciliophora density and diversity. Diurnal observation showed that the average minimum air and the maximum for air, water and pH in 12 noon and dissolved oxygen in 18 evening respectively. Totally 943 ciliophora were counted, out of which only 601 number were identified. The ciliophora identified were represented by seven species, six genus, five family, three suborder, four order and three classes. During the present study the population density of identified species was in the fallowing orders: Carchesium polypinum> Didinium nasutum> Aspidisca costata> Paramecium bursaria> Paramecium caudatum> Vorticella microstoma> Coleps hirtus. In the present investigation the minimum population density was recorded for Coleps hirtus which is an indicator for more polluted waters, while the other identified species are an characterized by less water pollution.
