const int trig = 2;
const int echo = 3;
const int triggerDist = 80;
long dura;
int dist;

void getDist() {
  // send "Get Distance" signal
  digitalWrite(trig, LOW);
  delayMicroseconds(2);
  digitalWrite(trig, HIGH);
  delayMicroseconds(10);
  digitalWrite(trig, LOW);

  // get travel time
  dura = pulseIn(echo, HIGH);
  // calculate distance
  dist = dura / 58;
}

void setup() {
  pinMode(trig, OUTPUT);
  pinMode(echo, INPUT);
  Serial.begin(9600);
}

void loop() {
  getDist();
  if (dist < triggerDist) {
    Serial.print("Algae Detected");
    return;
  }
  delay(100);
}