The growth and development of fish depend on the physicochemical properties of water, such as temperature, turbidity, concentration of hydrogen ions (pH), dissolved oxygen, total alkalinity, total hardness, nitrates, nitrites, etc. The article presents data on the hydrochemical regime of growing ponds of the farm “Rudnyky” of Lviv region. Studies have shown that the water quality indicators of growing ponds during the growing season are within the normative values and the water is suitable for fish farming. In the breeding ponds of the Rudnyky fishery, the water quality indicators fluctuated within the following limits, namely: the hydrogen index (pH) was within the maximum permissible concentrations (6.7–8.0). The content of dissolved oxygen in the water during the growing season was within normal limits (6.5 to 7.8 mg/l) and fully met the requirements for carp fish ponds, the alkalinity of the water was average and varied between 2.40 and 3.20 mg-eq/l, permanganate and dichromate oxidation varied slightly – 8.6–15.45 mgO/l and 25.6–40.50 mgO/l, which corresponds to the normative indicators for fish farming. The concentration of ammonium nitrogen (NH4+) in the growing ponds of the farm averaged 0.008–0,520 mg N/l, the content of nitrites and nitrates was 0.002–0.100 mg N/l and 0.060–0,520 mg N/l, respectively. The average concentration ranged from 0.10 mg P/l to 0.40 mg P/l of mineral phosphorus (PO4-3), which did not exceed the normative values. The amount of total iron in the water of the pond did not have high values, averaged 0.10–0.38 mg Fe/l, which was within the maximum allowable concentrations. The values of total hardness of water were determined as moderately hard and were in the range of 2.9–5.0 mg-eq/l. The salt composition of pond water was characterized by total mineralization, the ratio of ions and the content of chlorides, sulfates, bicarbonates. During the study period, the content of chlorides (Cl-) sulfates (SO4 2-); hydrocarbons (HCO3-), did not exceed the maximum allowable concentration. Among the cations in the pond water, calcium ions (Ca2+ ) predominated, their content averaged 28.2–80 mg Ca/l. In the studied pond, the concentration of magnesium (Mg2+) reached average values – 6.8–20.0 mg/l. The total mineralization of water was 300.4–440.4 mg/l. By the nature of the ionic composition, the water of the growing ponds belongs to the hydrocarbonate composition of the calcium group.
Comparison of Four Different Methods For the Determination of the Dissolved Oxygen in the Fish-Culture-Pond Water