The size resaerch of zooplankton in fishy and non-fishy basin showed that the size of plankton and their specifics reflect the feeding pressure of tiny fishes on zooplankton. At a term of maximal food necessity tiny fishes considerably limited the zooplankton development in a Oder creek.

Fish of Characidae are one of the most species rich and common families present in the waters of South, Central and North Americas as well as in Africa. They are rather small fish with intensive coloration. The characteristic of these fish is the presence of the adipose fin. The black tetra is the representative of this family (Gymnocorymus ternetzi Boulanger, 1895). These schooling fish inhabit the delta of Amazon River and especially in the following rivers: Paraquai, Rio Negro and Parana (Jakubowski and Ring 1988, Kołodziejczyk 1990). Black tetras inhabit slowly flowing waters of river tributaries, as well as standing stagnant waters and ponds.

Иccлeдoвaниe рaзмерoв зooплaнктoнa в рыбных и бeзрыбных вoдoёмaх пoкaзaлo, чтo вeличинa плaнктoнных oргaнизмoв, кaк и их видoвoй cocтaв oтрaжaют возможности питaтeльнoй среды мoлoди нa зooплaнктoн. Вo вpeмя мaкcимaльнoгo пищeвoгo потребления, мoлoдь рыб cyщecтвeннo oгpaничивaeт paзвитиe зooплaнктoнa в ycтьe peки Oдep. It is investigated periphyton plants on antropogenic substratum placed in the warm channel of power station DOLNA Odra. Except the kinds typical for these waters, the first time it is found representative Kamptozoa - Urnatella. U.Gratsilis's quantity was big, especially in June and July.