“Normal” Reference Ranges for Routine Water Quality Analysis
“Normal” Reference Ranges for Routine Water Quality Analysis
Parameter
Freshwater
Saltwater
Dissolved oxygen
Saturationa
Saturation
Carbon dioxide
<12 mg/L
<12 mg/L
pH
6.5–9.0
7.8–8.3
TAN (total ammonia nitrogen)b
0 mg/L
0 mg/L
Toxic un-ionized ammonia (NH3)b
0 mg/L
0 mg/L
Nitrite
0 mg/L
0 mg/L
Nitrate
<20 mg/L
<70 mg/L
Total alkalinity (carbonate fraction)
>100 mg/L CaCO3
>250 mg/L CaCO3
Total hardness (Ca and Mg primarily)
>20 mg/L CaCO3
>250 mg/L CaCO3
If source water is from municipal water supply:
Total chlorine (free chlorine + chloramines)
0 mg/L
0 mg/L
Free chlorine
0 mg/L
0 mg/L
a Dissolved oxygen in ponds will fluctuate on a diurnal basis. Concentrations <5 mg/L are dangerous. Mortality will be species-specific and related to time of exposure but may be observed at ≤4 mg/L. Oxygen saturation at room temperature (25°C [77°F]) and sea level will be 8.27 mg/L in freshwater and 6.75 mg/L in seawater (35 ppt or chlorinity of 20 ppt).
b Under most circumstances, freshwater fish can tolerate total ammonia concentrations <1 mg/L, whereas saltwater fish will usually tolerate TAN <0.5 mg/L. Un-ionized ammonia concentrations <0.05 mg/L are not considered harmful.
