Thanks! Yeah that is a pretty serious lens right there. I bought that lens when I sold my 400g acrylic setup
A buddy of mine has the 55-200mm non VR lens (it's almost the size of the standard 18-55mm). And it's pretty awesome to compare the size/weight of those two lenses, even though they have the same zoom level.
But I agree with Burto, stick with the basic 18-55mm lens and invest in some speedlights. They will transform your photos. The main reason to get big pro lenses is speed; the big fixed apertures at all zoom levels give you great low-light shots. I use these lenses for general photography, they're not strictly for aquarium photography. Mine stays at a constant f/2.8 whether it's at 70mm or 200mm. The kit lens on the other hand, can only go as big as f/4 at 55mm and f/5.6 at 200mm (the aperture gets smaller as you zoom).
When shooting fish, you want three things in your settings:
1) very fast shutter speed to freeze the motion and avoid blur (1/125th or faster)
2) lowest ISO possible for highest image quality (100-200)
3) small apertures to get the fish in full detail and avoid blur (f/8 - f/16). I like using my zoom lens in order to achieve the cool background bokeh you see in my shots
If you try and shoot at these settings, even with a big pro lens, the result will be a pitch black image. This is because you do not have enough light. This is where the speedlights come in. They give you an intense blast of light over the tank resulting in an awesome picture.
Take a look at Greenterras's photos. I believe he's still using the basic kit lens with his Canon DSLR, but he's using wireless speedlights. His photos are some of the best on this site.
So in conclusion, if you have $3-400 to spend, I'd get 1 or 2 speedlights (some models cost 2x that of others).
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