dimmer on a stantard fixture?

hey, on my 75 gallon i use a standard
two-bulb fourescent fixture, and i was wondering
if a dimmer will work on this?

ive never used a dimmer, and im not sure of the
format...is it just a box that plugs into the outlet,
and you plug your light of choice into that...orrrr?

any input will help, thank you ver much.
-andrew.

okay, thanks.