Too many duplicate photos

I'm not sure this thread is in the right category but I don't know where else to post it. For some reason I have numerous duplicate photos in my library. Some photos, I have 6 or 7 copies of. I want to delete all copies but the original but the problem is, they appear in many different places in my photo folder and there are 8,000 to go through as a result of this. Some are so similar that I don't know which dupe is which. Does anyone know of a simple way to search and find the photos and delete all the dupes without deleting the originals? I know this would free up a ton of space on my MacBook. Thanks for your help!

In iPhoto? Try this:

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