mwladdicted
Post Count D-M-S
The tank size does not make a difference to the lens you should get. Important is to ensure the macro lens can do 1:1 magnification - then it is considered a true macro lens and you can get really close. A 100mm lens will most likely focus further at 1:1 than a 60mm, though this depends on lens construction. For the aquarium I'd say 100mm is great - allows you to get nice shots of critters deeper in the tank, though I think price/availability is the bigger factor here.
Not sure what you're saying here? The lens size will make a difference. 100 mm well definately focus further than a 60mm and like I said; put more space between the subject and camera, from the lens I've used at least. I think 60mm are cheaper as well. His tank isn't even 20" deep. He could prolly get away with a 60. Just sayin...