Article
Dissolved Oxygen Monitoring for Fish and Shrimp Ponds: An IoT Guide for Malaysian Farmers
Fish and shrimp farmers know the fear of early morning. Dissolved oxygen in ponds often drops lowest just before dawn, after a night without photosynthesis. On a still, hot night, oxygen can fall to dangerous levels while everyone is asleep. By morning, the pond surface may be full of gasping fish or shrimp that stopped feeding.
IoT monitoring is one of the most practical technologies for Malaysian aquaculture because it watches the water continuously and can switch on aerators automatically.
Why dissolved oxygen matters so much
Fish and shrimp take oxygen from the water. When levels fall too low, animals become stressed, stop eating and may die. Oxygen levels are affected by water temperature, stocking density, algae, feeding, weather and time of day. Warm water holds less oxygen, which is a constant factor in tropical ponds.
The daily cycle is important. During the day, algae produce oxygen through photosynthesis. At night, algae and animals consume it. Cloudy days reduce oxygen production, so a cloudy day followed by a calm night can be risky.
What an IoT pond system monitors
A typical system includes:
- Dissolved oxygen probe: the most important sensor for most farms
- Water temperature: helps interpret oxygen readings and feeding decisions
- pH: affects animal health and the toxicity of ammonia
- Salinity or conductivity: relevant for brackish shrimp ponds
- Aerator status: confirms paddle wheels or blowers are running
- Power supply monitoring: alerts if electricity fails
Sensors connect to a controller near the pond, which sends data to a phone app through cellular networks or LoRaWAN.
Automatic aerator control
The biggest benefit is automation. When oxygen drops below a set level, the controller switches on aerators. When levels recover, it can switch some aerators off to save electricity. Running every aerator all night is expensive, while running none is risky. Sensor-based control finds the middle ground.
Set two thresholds: a lower level that turns aerators on, and a higher level that turns them off. This avoids rapid switching that can wear out motors.
Key takeaway: the most valuable alert on a pond farm is a power or aerator failure at night. Make sure it reaches someone who can act within minutes.
Probe care in real conditions
Dissolved oxygen probes need regular cleaning and calibration. Algae, mud and biofilm build up on the sensor and cause drifting readings. Optical sensors generally need less maintenance than older electrochemical types, but they still need cleaning.
Build a routine:
- Clean probes on a regular schedule, more often in ponds with heavy algae.
- Calibrate according to the manufacturer's instructions.
- Compare readings with a handheld meter periodically.
- Replace membranes or sensor caps as recommended.
- Log each maintenance visit so you can link changes in readings to cleaning.
A dirty probe can give falsely low or high readings. A falsely high reading is dangerous because aerators may not switch on when needed.
Placement in the pond
Oxygen varies by depth and location. Probes near aerators read higher than the rest of the pond. Place probes in a representative location, away from inlets and aerators, at the depth where animals spend most of their time. Large ponds may need more than one probe.
Mount probes on a stable float or post so they stay at consistent depth. Protect cables from rodents, birds and workers' equipment.
Power and backup
Electricity is the lifeline of an aerated pond. Monitor power at the controller and get an immediate alert if supply fails. Many farms keep a generator on standby and train workers to start it at night. A small battery backup for the controller and communications ensures that the alert itself is sent even when power fails.
Solar panels can power sensors and controllers in remote areas, though aerators usually need grid or generator power. For connectivity planning on remote sites, see our guide on SIM and connectivity for remote Malaysian sites.
Using data beyond alarms
Over time, oxygen and temperature data reveal patterns. You may see that oxygen crashes after heavy feeding on cloudy days, or that one pond always needs more aeration. This helps adjust feeding, stocking and aerator placement. Compare data with harvest results to understand what conditions give the best survival and growth. For simple ways to review data with your team, see using IoT data in weekly meetings.
Starting with one pond
If you manage many ponds, start with your highest-value or most problematic pond. Run the system for a full crop cycle. Track alerts, aerator hours and outcomes. This gives you real evidence to decide whether to expand and how many probes you need.
FAQ
How often should dissolved oxygen be checked?
Continuous monitoring is ideal, especially at night. Manual checks at dawn and dusk are a minimum if you do not have sensors.
Can one probe cover several ponds?
No. Each pond has its own conditions, so each needs its own probe for reliable automation.
Do I still need workers at night?
Yes. Sensors and automation reduce the burden, but someone must respond to power failures, equipment faults and emergencies.
Dissolved oxygen monitoring can be the difference between a good harvest and a lost crop. Invest in reliable probes, keep them clean, and make sure night alerts reach someone ready to act.