Rio 20HF loud noise

[LoveJC03]

Ordered a Rio 20HF off of Ebay the other day.. got it today, put in water and plugged it in.. it's VERY LOUD. Not sure if it's suppose to be. We have a Rio 2100 and it is very quiet.

Took it apart and noticed this little piece on the impeller...
http://i1164.photobucket.com/albums/q578/LoveJC03/Other/DSCN1309-1.jpg

Is it removable? ...will it make the sound quieter? Any advice is welcome!