The 21-year-old has failed to break into the first-team ahead of Darren Ward and Barry Roche and is more renowned for his penalty saves in the half-time entertainment.
He told the official website: "I'm looking forward to my month with Grantham. I will continue to train with Forest but it's a great chance for me to play a few games."
The German youngster could make his Town debut against Tiverton Town on Saturday.