“Normal” Reference Ranges for Routine Water Quality Analysis
Parameter | Freshwater | Saltwater |
|---|---|---|
Dissolved oxygen | Saturationa; > 5 mg/L | Saturation; > 5 mg/L |
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 |
Nitritec | 0 mg/L | 0 mg/L |
Nitrated | < 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 CaCO3c |
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 |
aDissolved 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). bUnder most circumstances, freshwater fish can tolerate TAN concentrations < 1 mg/L, whereas saltwater fish will usually tolerate TAN concentrations < 0.5 mg/L. Un-ionized ammonia concentrations < 0.05 mg/L are not considered harmful, with the caveat that there will be species-specific and situation differences in tolerance. cTest kits may only provide results in Nitrite-Nitrogen. Not generally measured in marine systems. dTest kits may only provide results in Nitrate-Nitrogen. | ||