Table 2 Water parameters (mg/l) and seasonal variations of heavy metals concentrations (mg/l) in three water samples per season of fish cultures in Kafr El-Sheikh governorate

pH value

8.03

7.33

7.62

7.5

7–8.5

Temperature

18 +  0.5 °C

20 + 0.5 °C

22 +  1 °C

25 +  1 °C

Chemical oxygen demand (COD) (mg/l)

10

20

30

35

≤ 10

Dissolved oxygen (DO) (mg/l)

5.05

4.59

4.6

4.3

≥ 5

Alkalinity (mg/l)

140

120

110

90

20–150

Total hardness (mg/l)

70

90

175

230

30–180 (Santhosh and Singh 2007)

Ammonia (NH₃) (mg/l)

1.1

3.6

3.2

4.8

0.5

Nitrite (NO₂) (mg/l)

0.42

0.3

0.4

0.3

< 0.2 (OATA 2008)

Cadmium

< 0.001

< 0.001

< 0.001

< 0.001

≤ 0.003

Copper

< 0.01

< 0.01

< 0.01

< 0.01

≤ 1

Lead

< 0.001

< 0.001

< 0.001

< 0.001

≤ 0.5

Zinc

< 0.001

< 0.001

< 0.001

0.59

≤ 2