Managing dissolved oxygen

Why oxygen matters most

Dissolved oxygen (DO) is the water parameter that kills fastest. Low oxygen slows feeding and growth, stresses stock and, when it falls far enough, causes mass mortality within hours, usually just before dawn.

Safe ranges

Most farmed fish and shrimp do best with DO above about 5 mg/L. Below about 3 mg/L stock is stressed and stops feeding; lower still is an emergency. Species differ, so set ranges for your own stock.

• Above 5 mg/L: good
• 3 to 5 mg/L: reduce feed, increase aeration, find the cause
• Below 3 mg/L: emergency, aerate and exchange water

The daily oxygen cycle

Algae produce oxygen in daylight and everything in the pond consumes it at night. DO is usually highest in the late afternoon and lowest just before sunrise. A dense bloom, cloudy weather or an algae crash can push the night-time low into danger.

• Measure at dawn as well as in the afternoon
• Cloudy days, high temperatures and heavy feeding all increase the risk
• A sudden change of water colour can signal an algae die-off

Aeration scheduling

Run aerators through the night and early morning, and longer as biomass grows. Position paddle wheels to keep water moving across the whole pond and away from sludge zones. Keep a backup power source or spare aerators for heavy-biomass ponds.

Feeding and oxygen

Uneaten feed and waste consume oxygen as they decompose. Feed in measured portions, check feeding trays, and cut feed when DO is low or stock is not eating.

How the portal helps

Record DO with each water reading from a phone, even offline. Readings outside your warning or critical limits raise an alert, and critical ones notify the team immediately (and by SMS when switched on). Trends per pond show when a pond is heading into trouble.