ESP8622 for my fish tank

fish_tank.ino

#include <Arduino.h>

#include <OneWire.h>
#include <DallasTemperature.h>

#include <ESP8266WiFi.h>
#include <ESP8266WiFiMulti.h>
#include <ESP8266HTTPClient.h>

#define ONE_WIRE_BUS 4

OneWire oneWire(ONE_WIRE_BUS);

DallasTemperature sensors(&oneWire);
DeviceAddress thermometer;

ESP8266WiFiMulti WiFiMulti;

float fetchTemperature() {
  sensors.requestTemperatures();
  return sensors.getTempCByIndex(0);
}

void setup() {
  Serial.begin(115200);
  sensors.begin();

  if (sensors.getAddress(thermometer, 0)) {
    sensors.setResolution(thermometer, 12);
  } 

  for(uint8_t t = 4; t > 0; t--) {
    Serial.printf("[SETUP] WAIT %d...\n", t);
    Serial.flush();
    delay(1000);
  }

  WiFiMulti.addAP("SSID", "PASSWORD");
}

void loop() {
  // Fetch temperature from sensor.
  float temperature = fetchTemperature();

  // Send data to Firebase.
  if((WiFiMulti.run() == WL_CONNECTED)) {
    HTTPClient http;
    
    http.begin("URL", 80, "/");

    String data = "{\"temperature\": " + String(temperature) + ", \"timestamp\": {\".sv\": \"timestamp\"}}";
    
    int httpCode = http.POST(data);

    if (httpCode) {
      if (httpCode == 200) {
        Serial.println("Data saved! :)");
        delay(1000 * 60 * 5);
      } else {
        Serial.println("Unable to save data to server: " + String(httpCode));
      }
    } else {
      Serial.println("No connection to server.");
    }
  }

  delay(1000);
}