Fish Pond Dissolved Oxygen and Water Quality Monitor with Dashboard

Fish die in ponds for one common, invisible reason: dissolved oxygen crashes overnight when algae and stock respire and no photosynthesis replaces it. Farmers discover it at dawn, when the fish are already floating. Handheld DO meters exist but nobody stands at the pond at 3 a.m. The engineering gap is continuous monitoring with automatic response — a probe that never sleeps, an aerator that starts itself at the configured threshold, and a dashboard that shows the pond's daily oxygen rhythm so the farmer learns the pattern, not just the alarm. This project builds that on an ESP32: a DO probe, pH probe and waterproof temperature sensor in the pond, a relay driving the aerator, and a dashboard with live curves, threshold bands and an event log.

1. The DO, pH and temperature probes sit in the pond (demo: aquarium tank) and the ESP32 samples them continuously.
2. Firmware applies the buyer's calibration constants and checks each reading against configured safe bands.
3. If dissolved oxygen drops below the start threshold, the aerator relay energizes; it releases only after oxygen recovers past the higher stop threshold (hysteresis).
4. Every reading and every aerator state change publishes over Wi-Fi to the dashboard.
5. The dashboard plots the curves with threshold bands and keeps the event log for the report.
6. Ammonia is entered as a manual test-kit reading alongside, since no low-cost continuous ammonia probe is used — stated honestly.

Tech stack:

• ESP32 development board (Wi-Fi telemetry)
• Dissolved oxygen probe + transmitter board
• pH probe + interface board
• DS18B20 waterproof temperature sensor
• Relay module (aerator control)
• Aquarium air pump (demo aerator)
• Single-page pond dashboard (HTML/JS)

• [Dissolved oxygen sensing] A DO probe measures oxygen continuously — the single most important pond parameter — with the safe band shown on the dashboard.
• [pH and temperature] A pH probe and waterproof temperature sensor complete the basic water-quality picture alongside DO.
• [Automatic aerator control] When DO falls below the configured threshold, the controller starts the aerator through a relay and stops it on recovery, with hysteresis to avoid chattering.
• [Pond-health dashboard] Live DO/pH/temperature curves, threshold bands, aerator state and a 24-hour rhythm view show the pond's daily cycle.
• [Night-dip profiling] The dashboard highlights the overnight oxygen dip, teaching the farmer when the pond is most vulnerable.
• [Event log] Aerator starts/stops, threshold crossings and sensor warnings are timestamped for the report.
• [Calibration procedure] DO and pH probes are calibrated by the buyer (air-saturated water and buffer solutions) with the steps documented.

• Working pond-monitor prototype (DO, pH, temperature probes, aerator relay, ESP32)
• Demo aquarium rig with air pump
• Complete firmware source code (sensing, calibration, aerator control, dashboard sync)
• Pond-health dashboard with curves and event log
• Circuit and wiring documentation
• Probe calibration procedures (buyer-run DO and pH calibration)
• Project report PDF (aquaculture water quality, control design, logged data from the buyer's run)
• PPT presentation for final review
• Viva Q&A preparation document (dissolved oxygen dynamics, pH, hysteresis control, calibration)

• Probe accuracy depends entirely on the buyer's calibration run; uncalibrated readings are indicative only.
• DO probes drift and foul with biofilm — the report includes a cleaning schedule; it is not a fit-and-forget sensor.
• Ammonia, the other critical parameter, has no continuous low-cost probe here; it is a manual test-kit entry, stated honestly.
• Demonstrated on an aquarium; a real pond needs weatherproof enclosures, longer cables and lightning care — future scope.
• Aerator control is threshold-based, not a variable-speed drive.