Dissolved oxygen requirements to fish

• Many species of fish can survive for varying periods at concentrations below 5 mg/L.
• A continuous low dissolved oxygen level affects fish by decreasing their resistance to disease, decreasing fecundity, inhibiting growth, and increasing fish’s susceptibility to other unfavorable conditions.
• Warm water fish would die if exposed for a few hours to less than 0.3mg/L dissolved oxygen.
• It is stated that 1 mg/L of dissolved oxygen is the minimum concentration necessary to support fish at rest for several hours and is exposed to less than 1.5 mg/L for several days, most fish will die.
• For best growth and development, warm-water and cold-water fishes require more than 5 mg/L and 8 mg/L oxygen, respectively.

Dissolved oxygen lacking conditions in the pond

• If too many fishes are stocked.
• If the weather is cloudy.
• If organic matter decomposes excessively/phytoplankton die-offs.
• If the water temperature is comparatively higher.

Signs of low dissolved oxygen in fishpond

• Fish come to the water’s surface and gulp air bubbles very frequently. This behavior is called piping.
• Fish aggregate at the water inlet.
• Fish don’t feed well or even stop feeding.