Investigations of natural ecosystems by only empirical methods usually are not possible due to their uniquity. This problem may be solved by combination of empirical and theoretical investigations. However traditional ecological models can not describe large complex ecosystems correctly. These models showed that stability of ecosystems should decrease with increasing their complexity. It contradicts with fact of existence in nature great amount of stability large complex ecosystems.

This paper is devoted to estimation of dependence of closed ecosystem stability on numbers of species in terms of adaptive metabolism model. In contrast with classical models, in considered one species consume nutrients in non-fixed proportion. Considered model ecosystem has two trophic levels: producers and consumers. With numerical analysis show that in term of it ecosystems stability may increase with increasing number of included species.