Memito, if I were you, I'd half that light! 440W is a heck of a lot of light, even on an established tank, on a newly set up 75 gal - you're asking for a major mess! As a matter of fact, even on an established tank, you'd be just fine with 220W. Even with 220, you'd better keep your co2 and ferts on target.
I hope you got some fast growers to your 'break-in' period. Give yourself a good start. I know a couple of people who started with a ton of light, and got so disappointed at their algae farm that they quit.