I used to run the large lumenbrite pendant over my 150 deep dimensions at about 15" off the water and got a pretty good spread. Started with a 400w and down sized to a 250w and still worked good. I also had 3 PowerBrite LED's on the ceiling beaming at a 45 degree angle to go right under the hanging pendant. Worked out nice and did not get a lot of light bleed on the side glass so the algae was not too bad.