unless your looking for more pretty white colours in your tank hehe:):)

You think three would be enough on a 7' long 30" deep tank @12" awl?

i think it all depends what you're trying to light up.

with 3 mounted parallel to my front glass i get no light on the glass (which is what i want) because i dont have rocks going directly to the glass.

if you have a 7 foot tank but only 5 feet of rock to light, then it'll work with 3 fixtures

I agree with MarkoD. In the last couple of months I helped with 2 300DD installations. Neither hobbyist went by the AI recommendations. One 300DD has 3, yes 3 modules, the other 300 DD set up started with 3 AI Modules but has since added two more. Both systems are outstanding.
The key was placement, height above water line, water parameters and supplemental coral feedings.
The AI modules have enough PAR to deliver results in an aquarium 36" deep. Your depth of 30" will not be an issue.

As for strength, I've had my 5 units 18 inches over the 225 (72,24,30deep) for 4 weeks now, and they are running at 70 white and 100 both blues for over a week now, everything is growing like mad, I did have some cyano on the sand for a bit, but I just broke out the Hanna checker and found out that my gfo needed to be changed, sitting at .22 phosphates..... So ditched the gfo and put in some foz down and the next day cyano almost gone..... So it wasn't the lights causing the algae, but an underlying problem of phosphates.....

Steve

I saw the tank at the store yesterday, SOL's or SOL blues?

they're all SOL blue now

One my 48x18 footprint I'm only planning on running 2. look into changing out your 40 degree optic lenses to something with more spread like 70 or 80. should reduce the spot light effect

Marco did you go with the blues?

Yeah I did. I didn't realize there was others