Reference Media

Hi all.
With FCP-X, I realized that by default my settings were set to copy media on import. This was making my FCP library files in the 300 to 400 gig range. I understand I'm working with video, and files will be large, but I would like FCP to reference the media in its place instead of actually copying it. I went to preferences > Import > and at the top under "Files" I checked the box that says "Leave in Place." I figured this would do the trick, however, it didn't seem to do what I thought it would. My library files are still just as big, and it seems like it is still copying my movie files instead of referencing them. Any suggestions or ideas on why this might be?

Thanks

Are you rendering effects in your project? This increases the Library size. If not necessary, you should periodically delete unused render files. See pic.