Thanks, Mike. Well, this tank is 24" wide and we have great coverage front to back. I did try them on a 36 inch wide tank and we had to have them 21 inches above the tank to get the spread from front to back and that just didn't work out as that was one of the older 250 watt model. I would imagine you could do it with the 400 watt model, but you would probably want to contact PFO as they can tell you how high up you'll need to place the lights for the spread. They were dead on with mine. Also, the lights are VERY bright at full white and full blue, so if you did have to hang them up a bit higher, I think you'd probably be fine.