Many species of zooplankton form dormant eggs, which is a widespread phenomenon in aquatic ecosystems [1]. This is a common way in which populations survive unfavorable environmental conditions. Dormant eggs are resistant to drying and freezing [7], and they retain viability during a long storage [9]; therefore, they play an important role in the dynamics and evolution of aquatic ecosystems [3]. Dormant egg formation is traditionally regarded as an adaptive response to adverse factors that are potentially lethal for a population. The fact that species inhabiting temporary water bodies are the most sensitive to the environmental factors confirms this hypothesis [2]. At the same time, dormant egg formation may serve as a mechanism for supporting species diversity in the ecosystems in a relatively stable environment. The long-term coexistence of many phyto- and zooplanktonic species, their numbers exceeding the number of growth-limiting factors, is a well-known phenomenon referred to as the planktonic paradox [10]. In aquatic ecology, this phenomenon is in conflict with an axiom of modern ecology, Gause’s principle, according to which, in stationary environment, one out of two species competing for the same resource becomes extinct. The conditions meeting this axiom are extremely rare in nature; hence, the species diversity in real ecosystems often contradicts Gause’s principle, which may seem a paradox. To explain this paradox, a concept has been developed suggesting that water column serves as a multi-dimensional ecological niche where coexistence of species competing for the same resource is possible due to nonuniformity of the medium and periodicity of processes. Dormant egg formation may be regarded as a mechanism that supports species coexistence. For example, Caceres has reported that two close Daphnia species differing in reproductive strategy coexist in the same lake [5]: one species has a diapause in its life cycle, whereas the other species has no diapause. We studied the results of species competition for the same resource to estimate the possibility of the coexistence of two zooplanktonic species with different reproductive strategies: a species that forms dormant eggs and a species that does not form them. In this study, we used a discrete model of cyclic reproduction in Cladocera, which had been developed previously [13]. This model simulates a laboratory Cladocera batch culture with a continuous flow of fresh media and nutrition. Species competition was modeled in the space of natural values of zooplankton growth rate (0.004‐0.04 h ‐1 ) [11]. The region of modeling was divided into 81 cells using a grid with a spacing parameter of 0.004 cm (Fig. 1). Ten calculations were made for each cell. The initial density of both populations was 0.18 (mg wet biomass) l ‐1 . The calculation continued until one of the populations became extinct. The results of competition (the death of one or the other population) and the total number of dormant eggs were recorded at the end of each calculation. The possibility of coexistence was evaluated under the assumption that, during seasonal zooplankton growth, reactivation of dormant eggs occurred at the beginning of the next season. It was assumed that only 10% or even fewer dormant eggs were capable of reactivating [6].