To competently assess a system’s design takes some practice; however, basic understanding and analysis can be accomplished by examining the component parts and their functions. Site visits are essential to understanding how a system has been constructed. In addition to assessing the design and functionality of a system, a site visit allows the opportunity to assess maintenance and cleanliness, both critical aspects of animal husbandry. The importance of a dissolved oxygen meter cannot be overstated when assessing an aquatic system. Oxygen concentration should be measured in the area housing the animals, and it should also be used to help identify areas prone to anoxia because of equipment problems, poor maintenance, or design flaws.
Water quality testing equipment is a requirement for aquatic practice ( See table A Summary of Water Quality Tests and Recommended Use). Good quality testing kits are commercially available at reasonable prices. Tests can be run quickly, providing data in a timely manner.
The basic parameters to be tested are:
temperature
dissolved oxygen
CO2
chlorine
chloramine
nitrite
nitrate
pH
total alkalinity
total hardness
salinity
A Summary of Water Quality Tests and Recommended Use
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 | Noa | 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 | Weeklyb | |
Nitrite-nitrogen | Measures nitrite-nitrogen; nitrite (NO2-) causes methemoglobinemia (especially in freshwater fishes) | Yes | Yes | Required | Weeklyb | |
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 | Monthlyc | |
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 | Nod | 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. | ||||||
Testing for freshwater and marine systems is similar; however, the total ammonia nitrogen (TAN) test often sold for freshwater use requires the use of Nessler’s reagent, which has two distinct disadvantages: it contains mercury and therefore must be treated as hazardous waste, and it does not work in marine systems. Alternatively, an ammonia test using an ammonium salicylate reagent is recommended. Chlorine test kits (free and total chlorine) are not included in many kits marketed to the aquaculture industry and need to be ordered separately.
Also, a copper test kit and a refractometer (to measure salinity) should be on hand for use in marine systems. If a practice has enough cases to warrant the investment, an electronic oxygen meter is strongly recommended. If working in a rural area where well water is commonly used, test kits for iron and hydrogen sulfide should be considered. For true specialty practices, investment in a saturometer for detection of supersaturation is also suggested.
