Pond water monitoring for fish and shrimp farms: oxygen, temperature and pH alerts

The problem: losses that happen while you sleep

"We lost a whole pond of fish in one night." Many fish and shrimp farmers have heard this or lived it. Dissolved oxygen in a pond usually falls during the night and is lowest around dawn, and in hot, cloudy, still weather it can drop to dangerous levels. By the time someone walks the pond in the morning, the damage is done.

Checking water with a handheld meter or test kit is valuable, but it only gives you a snapshot. A monitoring system watches continuously and warns you while there is still time to act.

Monitoring is a tool for good pond management, not a substitute for it. Stocking density, feeding, water exchange and advice from fisheries officers and experienced farmers still matter most.

What to measure

• Dissolved oxygen. The most important reading for preventing sudden losses, and the most demanding sensor. It needs regular cleaning and calibration, and quality varies a lot between products.
• Water temperature. Simple and reliable. It affects oxygen, feeding and how the fish behave.
• pH. Useful for spotting changes, but pH probes drift and need regular calibration.

Other values such as ammonia are usually checked with test kits. Continuous sensors for them exist, but they are harder to keep accurate in a pond, so start with the three above.

Safe levels depend on the species, the stage of growth and local conditions. Set your alert levels with a fisheries expert rather than copying numbers from the internet.

How a pond system is put together

1. Sensors at a representative depth, away from the direct flow of the aerator, on a float or a fixed post.
2. A weatherproof controller on the bank that reads the sensors and stores the data.
3. Power, often a small solar panel with a battery, so monitoring continues through power cuts.
4. Connectivity, usually a mobile SIM. Check the signal at the pond itself before choosing; rural coverage can be patchy. Readings should be stored on the device and sent when the network returns, and you should get an alert if the device goes silent.
5. Alerts to two or more phones by SMS or call, plus a siren or light at the farm for whoever is on duty at night.
6. Aerator control, if you want it. The system can switch aerators on when oxygen falls below the level you set. This must be wired by a qualified electrician, with a manual switch that always overrides the controller.

Practical problems to plan for

• Fouling. Algae and mud build up on sensors. Someone must clean them on a schedule.
• Theft and damage. Equipment on a pond bank needs secure mounting.
• Lightning and water. Proper enclosures, earthing and cable routing matter. Anything connected to mains power is a job for a qualified electrician.
• Power for the aerators. Automatic control means nothing if the aerator has no power during an outage. Plan generator backup, and get an alert the moment mains power fails.
• Trust, but verify. Compare sensor readings with a handheld meter regularly.

What the farmer decides, and where an expert helps

You decide which ponds matter most, the alert levels (with your fisheries adviser), who responds at night and what they do. An IoT developer helps choose sensors that suit your ponds, build the controller, set up solar power and connectivity, and design the alerts and aerator logic, working alongside your electrician. This is part of my IoT device development work.

A first step that fits the season

Before the hot season, start with one high-value pond: one oxygen sensor, one temperature sensor, alerts to two phones, a siren at the farm and a weekly routine of cleaning and checking against a handheld meter. Run it for a full season before adding more ponds. The approach in starting with an IoT pilot applies here too. If you want to plan it together, get in touch.