Aquaponics Automation: Fish Tank and Plant Bed Monitoring

Aquaponics automation combines fish tank and plant bed monitoring into an integrated system that maintains optimal conditions for both aquatic life and plant growth. Aquaponics — the symbiotic cultivation of fish and plants — is growing rapidly in India as an efficient food production method using 90% less water than conventional farming. This guide covers building a complete automated aquaponics monitoring system with ESP32, water quality sensors, and automated pump control.

Table of Contents

• Aquaponics System Basics
• Critical Water Parameters to Monitor
• Components Required
• Circuit and Wiring
• ESP32 Monitoring and Control Code
• Automation Logic
• Aquaponics in India
• Frequently Asked Questions

Aquaponics System Basics

An aquaponics system cycles water between the fish tank and plant grow beds:

1. Fish produce ammonia-rich waste
2. Beneficial bacteria (Nitrosomonas) convert ammonia to nitrites, then to nitrates
3. Plants absorb nitrates as fertiliser — water is cleaned
4. Clean water returns to fish tank

This nitrogen cycle requires maintaining tight parameter ranges. A single failure — pump stoppage, temperature spike, pH drift — can kill both fish and plants within hours. Automated monitoring and alerts prevent catastrophic losses.

Critical Water Parameters to Monitor

Components Required

Full aquaponics monitor parts list:

• ESP32 development board
• DS18B20 waterproof temperature probe (for water temperature)
• pH sensor module (analog, requires calibration)
• TDS/EC sensor (for nutrient level monitoring)
• Ultrasonic sensor HC-SR04 (waterproof variant) for tank level
• 2-channel relay module for pump and aerator control
• Air pump (for dissolved oxygen aeration)
• Water circulation pump (12V submersible)
• OLED 0.96″ display (for local status)
• Buzzer (emergency alarm)

Circuit and Wiring

Sensor connections:

• DS18B20 data -> GPIO4 (with 4.7k pullup to 3.3V)
• pH sensor AOUT -> GPIO34 (ADC1_CH6)
• TDS sensor AOUT -> GPIO35 (ADC1_CH7)
• HC-SR04 TRIG -> GPIO26, ECHO -> GPIO25 (use JSN-SR04T waterproof variant)
• Relay IN1 -> GPIO27 (water pump), Relay IN2 -> GPIO14 (air pump)
• OLED SDA -> GPIO21, SCL -> GPIO22 (I2C)
• Buzzer -> GPIO13

Keep pH and TDS sensor probes in separate compartments to avoid cross-interference. Clean pH probes weekly with electrode cleaning solution. Store pH probes submerged in KCl storage solution when not in use.

ESP32 Monitoring and Control Code

#include <Wire.h>
#include <OneWire.h>
#include <DallasTemperature.h>
#include <Adafruit_SSD1306.h>
#include <WiFi.h>

OneWire oneWire(4);
DallasTemperature tempSensor(&oneWire);
Adafruit_SSD1306 display(128, 64, &Wire, -1);

#define PUMP_PIN   27
#define AIR_PIN    14
#define BUZZER_PIN 13
#define LEVEL_TRIG 26
#define LEVEL_ECHO 25

const char* ssid = "AquaFarm";
const char* pass  = "yourpassword";

// Parameter thresholds
const float TEMP_MIN = 20.0, TEMP_MAX = 30.0;
const float PH_MIN   = 6.5,  PH_MAX  = 7.5;
const float TDS_MIN  = 300,  TDS_MAX = 1200; // ppm
const float LEVEL_MIN_CM = 10; // Alert if tank too low

float readPH() {
  int raw = analogRead(34);
  float v = raw * 3.3 / 4095.0;
  return -5.70 * v + 21.34; // Calibration values
}

float readTDS() {
  int raw = analogRead(35);
  float v = raw * 3.3 / 4095.0;
  float ec = (133.42 * v * v * v - 255.86 * v * v + 857.39 * v) * 0.5 / 1000.0;
  return ec * 640; // Convert mS/cm to ppm
}

float readWaterLevel() {
  digitalWrite(LEVEL_TRIG, LOW); delayMicroseconds(2);
  digitalWrite(LEVEL_TRIG, HIGH); delayMicroseconds(10);
  digitalWrite(LEVEL_TRIG, LOW);
  long dur = pulseIn(LEVEL_ECHO, HIGH, 30000);
  return dur * 0.017; // Distance in cm (speed of sound / 2)
}

void checkAlarms(float temp, float ph, float tds, float level) {
  bool alarm = false;
  if (temp < TEMP_MIN || temp > TEMP_MAX) { Serial.println("ALARM: Temperature!"); alarm = true; }
  if (ph < PH_MIN || ph > PH_MAX)         { Serial.println("ALARM: pH!"); alarm = true; }
  if (tds < TDS_MIN || tds > TDS_MAX)     { Serial.println("ALARM: TDS!"); alarm = true; }
  if (level < LEVEL_MIN_CM)               { Serial.println("ALARM: Low water level!"); alarm = true; }

  if (alarm) {
    for (int i = 0; i < 3; i++) {
      digitalWrite(BUZZER_PIN, HIGH); delay(300);
      digitalWrite(BUZZER_PIN, LOW); delay(200);
    }
  }
}

void setup() {
  Serial.begin(115200);
  Wire.begin(21, 22);

  tempSensor.begin();
  display.begin(SSD1306_SWITCHCAPVCC, 0x3C);
  display.clearDisplay();

  pinMode(PUMP_PIN, OUTPUT);
  pinMode(AIR_PIN, OUTPUT);
  pinMode(BUZZER_PIN, OUTPUT);
  pinMode(LEVEL_TRIG, OUTPUT);
  pinMode(LEVEL_ECHO, INPUT);

  // Default: pump and aerator on
  digitalWrite(PUMP_PIN, LOW);  // Relay active LOW
  digitalWrite(AIR_PIN, LOW);

  WiFi.begin(ssid, pass);
  Serial.println("Aquaponics Monitor Ready");
}

void loop() {
  tempSensor.requestTemperatures();
  float waterTemp = tempSensor.getTempCByIndex(0);
  float ph        = readPH();
  float tds       = readTDS();
  float level     = readWaterLevel();

  checkAlarms(waterTemp, ph, tds, level);

  // Display on OLED
  display.clearDisplay();
  display.setTextSize(1);
  display.setTextColor(SSD1306_WHITE);
  display.setCursor(0, 0);
  display.print("Temp: "); display.print(waterTemp, 1); display.println(" C");
  display.print("pH:   "); display.println(ph, 2);
  display.print("TDS:  "); display.print(tds, 0); display.println(" ppm");
  display.print("Level:"); display.print(level, 0); display.println(" cm");
  display.display();

  Serial.printf("T:%.1fC pH:%.2f TDS:%.0fppm Level:%.1fcmn",
    waterTemp, ph, tds, level);

  delay(30000); // Read every 30 seconds
}

Automation Logic

Beyond monitoring, the system automates key processes:

• Timed pump cycles: Media-bed aquaponics uses flood-and-drain cycles (15 min on, 45 min off) to oxygenate roots
• Low water auto-refill: When level drops below threshold, open solenoid valve to top up from reserve tank
• Temperature response: If water temperature exceeds 30 degrees C, activate chiller or increase aeration rate
• pH dosing: Auto-dose small amounts of food-grade acid (phosphoric acid) when pH drifts above 7.5
• Feed timer: Automatic fish feeder relay on schedule (3x daily)

Aquaponics in India

Aquaponics is gaining traction across India:

• Urban farms (Bengaluru, Pune, Mumbai): Rooftop aquaponics for fresh fish and greens — local premium market
• ICAR research stations: Tilapia-vegetable systems demonstrating 60% higher protein production per square metre vs conventional farming
• Northeast India: Freshwater fish (Rohu, Catla) combined with rice using traditional Dhap farming integrated with IoT
• Arid regions (Rajasthan, Gujarat): 90% water saving vs soil farming — critical for water-scarce areas

Frequently Asked Questions

What fish species work best for aquaponics in India?

Tilapia (Nile) is the most popular — fast-growing, temperature-tolerant (20-32 degrees C), disease-resistant. Common carp, Rohu, and Magur (catfish) are also used. Trout requires cold water (12-18 degrees C) and is suitable for Himachal and Uttarakhand.

How accurate are the cheap pH sensors for aquaponics?

Analogue pH sensors (BNC-type, Rs 300-500) are accurate to ±0.1-0.2 pH units after 2-point calibration with pH 4.0 and 7.0 buffer solutions. Recalibrate every 2 weeks. For research-grade monitoring, invest in Atlas Scientific EZO-pH module (more stable, I2C interface).

Can I run aquaponics on solar power?

Yes, but size the system carefully. Pumps run 15-45 minutes per hour on average. A 100W solar panel with 100Ah battery can run a 50W pump system through cloudy days. Add a battery low-voltage cutoff to prevent deep discharge.

What is the minimum viable system size for commercial aquaponics?

For a viable commercial operation in India, minimum 1000 litres fish tank with 20 square metre grow beds. This supports 50-80 kg fish and 200-300 plants simultaneously, generating Rs 15,000-25,000/month revenue from mixed produce.

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