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Veterinary

Tables

A Summary of Water Quality Tests and Recommended Use

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Parameter	Purpose	Freshwater	Saltwater	Required?	Frequency
Dissolved oxygen¹	Determines concentration and percent saturation of oxygen gas in solution	Yes	Yes	Required	Daily
Temperature	Many fish are susceptible to infectious disease outside a narrow temperature range	Yes	Yes	Required	Daily
Salinity	Measures the salinity of water which is critical for marine systems	No^a	Yes	Required	Daily
pH	Determines acidity or alkalinity of the water; scale of 1–14	Yes	Yes	Required	Daily
Carbon dioxide	Measures concentration of carbon dioxide gas in solution	Yes	Yes	Recommended	Monthly, or whenever fish ar sick
Total ammonia nitrogen (TAN)	Measures combined ammonia (NH₃) and ammonium (NH₄⁺); unionized ammonia (NH₃) is calculated	Yes	Yes	Required	Weekly^b
Nitrite-nitrogen	Measures nitrite-nitrogen; nitrite (NO₂^-) causes methemoglobinemia (especially in freshwater fishes)	Yes	Yes	Required	Weekly^b
Nitrate-nitrogen	Nitrate (NO₃^-) accumulates in systems due to less water change; contributes to goiter; may be harmful to some fish at high concentrations; harmful to some invertebrates	No	Yes	Recommended	As needed
Total alkalinity	Measures buffering capacity; primarily carbonates; required for biological filtration; essential for calculation of copper sulfate treatment in freshwater systems	Yes	Yes	Required	Monthly^c
Total hardness	Measures divalent earth minerals; primarily calcium and magnesium	Yes	No	Recommended	Monthly
Chlorine, free	Measures free chlorine in water from municipal water treatment	Yes	Yes	Recommended	As needed
Chlorine, total	Measures total chlorine (free chlorine + chloramine) from municipal water treatment	Yes	Yes	Recommended	As needed
Copper ion (free and total)	Measures free copper ion (Cu²⁺) in solution; essential for titrating copper treatments in marine systems	No^d	Yes	Required	As needed
Saturometer	Measures total gas pressure; used to calculate percent saturation of nitrogen gas for confirmation of supersaturation ("gas bubble disease")	Yes	Yes	Optional	As needed
Hydrogen sulfide	Measures hydrogen sulfide in solution (most commonly from well water source); "rotten egg" smell for those who can smell it	Yes	Yes	Optional	As needed
Iron, total (Fe)	Measures total iron in solution (most commonly from well water source)	Yes	Yes	Optional	As needed
^aSalt is frequently added to freshwater systems in concentrations up to 5 g/L; monitoring is recommended in these situations.
^bIf ammonia or nitrite are detectable, the frequency of monitoring should be increased to daily. Daily monitoring is also recommended during the startup phase of a new biological filter or recirculating system.
^cIf pH of the system water is below pH of source water, alkalinity should be checked.
^dThe copper ion test kit will work in freshwater systems in which there is a need to measure free copper ion, such as a system in which the water supply is from copper pipes. It is not routinely used in management of freshwater systems but is essential for managing copper treatments in marine systems.