@Lisa no just about 80% of it
I can only second the points Byron already mentioned. I have all my tanks lights dialed way down (Eg instead of 2x30w over my 55g 1x30w, full spectrum of cause).
I can also only double underline the algae point Byron made, while this stuff thrives of many factors mixed I had found way back in the day when I had real high end lights (because I thought it was needed when really its not) I always had algae of various kinds, sometimes more sometimes less; I don't have this issue any more now since I have lower end lights.
As a direct Sword example:
I planted my 55g last Nov '09 with 2 Amazon Swords, about 6-8" with maybe 3-4 leaves when I bought them.
Now today Sep '10 these very 2 Swords measure abut 17-18" and are extremely bushy.
This is how they grew with my low lights, no ferts and 9 out of 10 days my floating plants cover the entire tank side-side and back-back unless I just get lucky and mail some off to hobbyists here (which does not happen often).
I can gladly show you some before-after pictures of the Swords for comparison.
Also bare in mind other plants, I had found plants like various Crypts or Ludwigia to thrive much better under less light/ light filtered by floating plants then without.