German goes straight into the Gills squad to face Oxford on Tuesday evening.
The 21-year-old signed an 18-month deal with the Bees in January last year following a trial and joined the north London club's development squad.
The former QPR trainee has scored once in four appearances for Uwe Rosler's team this season.
He has also had spells at Aldershot, Southend, Yeovil and Stockport during his short career.
