Studying of flora and fauna of the Chereksky reservoir takes a special place in hydrobiological researches which are carried out by the faculty of veterinary medicine and biotechnology in KBGAU named after V.M. Kokov. The quantitative analysis of links of a trophic chain of the reservoir indicates low-study of relationship of water organisms. These are primarily phytophilous species closely connect-ed with flora, biologically using them as a substra-tum for movement, construction of lodges, and lay-ing eggs. Studying biological features of Candonidae as the main producer of the Chereksky reservoir, we found out that spring population was presented by exclusively sexually mature females who since the beginning of April until the middle of May laid eggs in the soil and then perished. The first young individuals appeared at the beginning of May, and to the middle of July larvae 0.15- 0.72 mm long appeared. From the second half of July and almost until the end of November larvae of advanced age (length of 0.78-0.85 mm) met. The attempts to define the sex of larvae of the first and the subsequent stages had no success; external distinctive signs had not been found yet. Crusta- ceans 0.1-0.83 mm long already had bodies of re-production: pair of ovaries at the female and four pairs of semen canals at the male. Individuals of the sizes of 0.88-0.95 mm met in a reservoir at the beginning of August and to the middle of Septem-ber. The first were males (on August, 16) ripening slightly earlier than females and then females (on September, 5). From now on there is a pairing of ostracods which last to the middle of December. By the end of December males perish. And mature females live during the whole winter without breed- ing which is evidenced by the absence of juveniles in the winter samples.