Sure does. Now I assume because you said 18 inch, you have a 55 cube. The LFS in my area has one of these set up really nicely with something like 80 watts of power compacts on it. Theirs is heavily planted so that much wattage is appropriate. Are you planning on having plants or just want to light it up? Either way,
THIS is what they were using.
Now if I'm wrong in assuming the length of your tank, then there are definitely other options for longer lights.