Macro lens or extension tubes?

[Curly68]

Hi, I love taking pictures of my fish and have an old 100mm f2.8 macro lens. I find this focal length a bit too long sometimes and was thinking about the 60mm EF-S lens instead for my 40D. Then someone told me about the Kenko extension tubes. He uses them with his 70-200 F4L with some good results.
What would you suggest for these pics?
Many thanks

[airfrogusmc]

Both...