Water Quality and Environment

However, water quality is the first most important limiting factor in hatchery and grow-out production of fish. It is also the most difficult production factor to understand, predict and manage. Water is not just where the fish live. Its quality directly affects feed efficiency, growth rates, the fish’s health and survival. Most fish kills, disease outbreaks, poor growth, poor feed conversion efficiency and similar management problems are directly related to poor water quality.

Water quality refers to anything in the water, be it physical, chemical or biological that affects the production of fish. The objective of a fish holding facility is to manage the water quality to provide a relatively stress free environment that meets the physical, chemical and biological standards for the fishes normal health and production performance.

Levels of hatchery and grow-out water quality is a product of:

  • the quality of water at the water source,
  • the quality of the pond soils and immediate environment,
  • production technology
  • management procedures employed

The Water Quality Requirements for Tilapia and Catfish

Low water levels at high stockings in grow-outs and low flow rates through hatching and rearing troughs allow waste products to accumulate which may quickly cause deterioration of water quality through ammonia build up.
The key water quality parameters for hatchery production are temperature, oxygen, pH, alkalinity, hardness and nitrogenous waste. However, due to the dynamics within the pond environment and water source, they fluctuate daily depending upon photosynthesis of aquatic plants like algae, the production and management technology employed and local weather conditions.

 

Variable

Desired level

Problem

Temperature

28-30°C for optimum growth

25-27°C for optimum spawning and embryo development

too low

 

 

too high

Dissolved oxygen

> 4.0 mg/l

too low

pH

6.5-9.0

 

Carbon dioxide

<15 mg/l

too high

Total dissolved gases

delta P less than 40 mmHg

too high

Calcium hardness

more than 20 ppm as CaCO3

too low

Ammonia (un-ionized)

less than 0.05 ppm NH3-N

too high

Iron

less than 0.5 ppm total iron

too high

Hydrogen sulfide

<1.0 mg/1

 

too high

Salinity

<5ppt