The 21-year-old had been on loan with Girona since the beginning of the season but only went on to make four appearances for the Spanish side.
Moreno arrived at City in August 2016 from Colombian side Atletico Nacional in a deal worth £4.75 million.
He has failed to make an appearance for the first team and has also spent time on loan with Deportivo.
Moreno departed his native Colombia after winning the Copa Libatadores with Atletico Nacional, which is the South American equivalent of the Champions League.
He has made eight appearances for the Colombian national team, scoring once.