{"date": "11/21/2018", "nick": "abcd"}

const xUrl = 'https://xxxxxx.firebaseio.com/usuarios.json?orderBy="nick "';
     return this.http.get (xUrl) .pipe (
       map (res => {
         return res;
         console.log (res);
        })
     );

-LRqtDl09Sc1J4K4IOln:
      date: "11/21/2018"
      nick: "abcd"