Conversion Tools for Temperature, Ammonia, Oxygen Saturation, Volume and Area

To survive, grow, and reproduce, fish require quality water. Before starting an aquaculture business, take tests of several physical and chemical parameters of your water source. If these initial tests are acceptable, then only routine analysis of key chemical parameters will be needed.

Daily or Weekly (simple)

Many of the routine chemical parameters conducted daily can be assayed using relatively inexpensive test kits or meters.

Dissolved Oxygen

Dissolved oxygen is one of the most critical chemical parameters in aquaculture. More fish die from low dissolved oxygen levels than from any other factor. Oxygen solubility tables (salinity and elevation) are provided for reference.

Nitrogen Compounds

Nitrogen compounds consist of nitrogen gas dissolved in water and waste products produced through fish metabolism. These include ammonia, nitrite, and nitrate.

  1. Nitrogen Gas (N2)
    Nitrogen is a gas dissolved in water. Nitrogen gas levels should not exceed 110% of saturation. Nitrogen gas poses a potential problem from deep wells or hatcheries with leaky water lines.
  2. Ammonia
    Ammonia results from the breakdown of fish feed and wastes. It is present in two forms, ionized (NH4+) and un-ionized (NH3). The un-ionized ammonia concentration is a function of pH and temperature. Acute un-ionized ammonia toxicity occurs at temperatures of 0.6 mg/L. Chronic exposure to as little as 0.06 mg/L of the total ammonia concentration in the un-ionized form is toxic to warm water species such as catfish. An ammonia concentration table is provided.
  3. Nitrite (NO2-)
    Nitrite is an intermediate product in the breakdown of ammonia to nitrate (nitrification). Nitrite levels greater than 0.60 mg/L or 10 times higher than the toxic threshold for un-ionized ammonia is toxic to fish.
  4. Nitrate (NO3-)
    Nitrate is the final breakdown product in the conversion of ammonia to nitrate. Nitrate is relatively nontoxic to fish at concentrations up to 3.0 mg/L.

Relationships

Ammonia, nitrite and nitrate contribute to the total nitrogen concentration found in water.  Most water test kits for nitrogen are expressed in terms of total ammonia nitrogen (TAN).

pH

pH is the measure of the hydrogen ion concentration-acidity-of water. pH is measured on a logarithmic scale of 1-14 with 7 being neutral, neither acidic or basic.

Alkalinity

Alkalinity is usually water’s capacity to buffer against wide pH swings. Normally, alkalinity is a measure of carbonates, bicarbonates, and hydroxyl ions. Alkalinities in freshwater should be between 40 - 400 mg/L.

Hardness

Hardness is usually the measure of calcium and magnesium. Hardness levels should be no less than 40 mg/L.

Carbon Dioxide

Carbon dioxide is a byproduct of respiration in fish and algae. High CO2 levels can affect the fishes’ ability to properly utilize oxygen and can also depress the pH of the water.

Temperature

Fish are cold-blooded animals (pokiothermic) and take on approximately the same temperature as their surroundings. Temperature affects the growth and survival of fish because the metabolic rate in fish doubles with every 18°F increase in temperature. Fish are generally categorized into warm water, cool water, and cold water based on optimal growth temperatures.

Hydrogen Sulfide

Hydrogen sulfide is a dissolved gas found in some water sources or from anaerobic breakdown of waste products. Hydrogen sulfide has an odor similar to that of rotten eggs. Hydrogen sulfide is extremely toxic to fish and should not be present in water. Aeration is a simple way to remove hydrogen sulfide from water.

Total Suspended Solids

Solids in the water are made of two types, suspended and settleable. Suspended solids are sometimes referred to as turbidity and result from clay particles in the water. Settleable solids are a result of the buildup of fish wastes. The total suspended and settleable solids level should be maintained less than 80 mg/L. Excess solids may irritate the fishes' gills, interfere with photosynthesis, or smother fish eggs.

Chlorine

Chlorine is used as a disinfectant in aquaculture and drinking water. Chlorine levels should be less than 0.03 mg/L. Sodium thiosulfate applied at 1 mg/L for each mg/L of chlorine will neutralize chlorine.

Semi-Annually or Annually (complex)

More complex water quality parameters may be sent to a commercial laboratory for analysis. Parameters which should be checked prior to constructing an aquaculture facility and then on a semi-annual or annual basis are: