Sure, no prob, glad it helped you =)
You will need:
Canon EF 100mm f/2.8 macro &
Kenko Extension Tube Set (review). I'm not too sure about the price though.
For flash.. ehh.. What camera body are you using? If you use a 30D / 40D / 50D camera, there is a PC sync port. If you don't and you're using 350D/400D/450D.. then uhh.. just try with your 580EXII mounted on the camera, direct flash lor. Cannot do anything else, unless you invest in wireless radio triggered flash (where you will have to work your flash in manual).
The macro-twin-lite flash setup would be awesome if you don't just use the setup for shrimp / aquarium shooting, that is take pics of insects too. The closer you get to an insect, the better the macro flash will perform. Do note that it is super expensive, so if I were you, I'd just try with the 580EXII alone. Infact, you can try to get a stofen omnibounce so that the light is distributed in all directions, so some will hit the shrimp.
Talking about magnification, I'm not sure. You see, in macro photography terms, we talk in ratios. 1:1 means the size of the object is the same as the image on the sensor. The bigger the left-hand-side number, the larger the magnification, meaning the image is bigger. I'm not sure how things work out, but yes, if it's 10cm with extension tubes instead of 30cm, you will definitely get to see the shrimp to be way bigger. So you can see how its crap looks like, if it's translucent.
The extension tube is like another lens. Basically you mount the extension tube(s) to your camera first, then you mount your 100mm macro. Do note that extension tubes make your camera short sighted because the lens is further away from the sensor, so it can't focus to infinity. Meaning that with the extension tubes, your macro lens can't focus on the wall across the room, but only on near things. Get it?
You can definitely take something like the eye shot.. if you have:
#1 your setup above
#2 a willing person who doesn't mind to become blind from flash
#3 a willing person who knows how to stay still
#4 lots and lots of time for those "ALAMAK, BLUR LA, CAN LET ME SHOOT AGAIN?!" moments, because, frankly, those shots are quite difficult to pull off using reverse macro.
Oh, and even though you said you would need autofocus, I really recommend you to use manual focus unless your aquarium lighted up extremely well.
Use f/8 - f/11 aperture for shooting, and up the ISO accordingly.
Cheers
Zexun