Problem moving bottom part of Stream impellor

[reefkeeper1]

I soaked one of my Tunze Streams overnight in vinegar, and it did a great job of cleaning the outside of the Stream and the main impellor assembly. I tried removing the very bottom piece of metal that sits on the rubber o-ring with my wife's knitting needle, but I wasn't able to extract it. Nevertheless, the main impellor assembly is clean and still spins, so I'm okay for now. I was wondering if anyone has any suggestions on how to remove that bottom piece.

 

[rvitko]

Their are no metal pieces, the bottom piece is a blend of graphite and plastics. The magnet should spin in this track, if it has to drag this piece it doesn't tend to run properly and uses alot of power. A small slotted screwdriver and a longer soak in straight vinegar should seperate it.