#define TANK_SENSOR 8
#define PUMP 5

void setup() {
  pinMode(TANK_SENSOR, INPUT_PULLUP); // sensor with pull-up
  pinMode(PUMP, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  int tankStatus = digitalRead(TANK_SENSOR); 
  // HIGH = FULL, LOW = EMPTY

  if (tankStatus == HIGH) {
    Serial.println("Tank is FULL");
    digitalWrite(PUMP, LOW);   // turn OFF pump
  } else {
    Serial.println("Tank is EMPTY");
    digitalWrite(PUMP, HIGH);  // turn ON pump
  }

  delay(500);
}