The urban lakes are interesting systems because recreative, cultural and stetics places, by another way, they are important to several kinds of organism like Poecilia reticulata; it has a high tolerance to several environmental changes and its reproducing is more easy. The main goals of this work were: to determinate changes about abundance and biomass of Poecilia reticulata into Tezozomoc’s Park lake; and to achieve the growth equation. Each month were taken samplings, to July of 2000 to June of 2001, in three work stations into the lake. Depth, transparency, alkalinity, hardness, pH, conductivity, temperature and turbied were obtained by conventional methods. The biological samplings, the fishes, were captured using a spoon net of rectangular shape 100x50 cm (area 0.5 m²). The fishes were introduced into formalin to 10 % and, after that, carried to laboratory. Then, they were to weigh on digital scale and measured with a Vernier to standard length (mm). All this several parameters were used to know about abundance and weight to each work station and, growth equation like Von Bertalanffy model were obtained to all. The water is warm, muddy, alkaline and hard, apart from shallow. The highest abundance (6148 organisms) and biomass (677.28 g) had have work station 1 because people throw food waste. July (1,483 org.) and August (1,252 org) had highest abundance however, August (145.12 g) and March (138.63 g) had highest biomass. The condition factor highest were in March (0.03) because gravid female and adult male. Finally, about growth model, maximum length was 61.55 in the same way growth rate was 0.2987 as well as natural systems.