The huge number of pike, perch and roach has been safely rehomed further down the Grand Union Canal at the iconic attraction near Market Harborough.
The engineering marvel will be drained of water until the spring after the far-reaching blueprint was backed by Harborough District Council.
A Canal & River Trust spokesman said: “The fish rescue went well.
“Now with the fish safely out of the way we’ll be able to get on with the vital job of replacing some of the lock gates.”
He said people will be given the fascinating chance to explore the drained locks over the next few weeks.
“It’s a really exciting time at Foxton with the works themselves and a programme of winter works weekends set to begin in February,” said the Newark-based spokesman.
“They will give members of the public the opportunity to walk down to the bottom of a drained lock.
“It’s a rare opportunity for people to see the site in a whole new light.
“They should get a real appreciation for the fantastic heritage of the locks and the work that the Canal & River Trust and its volunteers does to keep things working the way they should.”
As part of the radical facelift, oak gates will be replaced on five of the 10 locks, brickwork in the lock chambers will be repaired and new lock ladders installed.
The massive Canal and River Trust operation is set to be completed by March.
Built between 1814 and 1900, Foxton Locks is home to two magnificent feats of engineering.
As well as the longest and steepest staircase locks in the UK, the 19th century site also boasts the inclined plane, an incredible piece of Victorian engineering.
More than 4000 boats travel through the ever-popular flight of locks every year and about 300,000 visitors flock to enjoy this unique landmark.