I recommend rowaphos because when it's used up it will not leach back into the water. It comes with a filter bag you can put anywhere in a high flow area (like your sump).
I agree with chilwil. I had the same prob with algae and finally got some rowaphos and the problem cleared up immediatly. I haven't had a problem since.
I had a tank that size on my main floor with a basement beneath which is pretty much like a second floor and didn't have a problem. I did have it against an outside wall however. Hope this helps.
There are fans in the fixture but they are just to cool the fixture. I have moved them a little higher but I still get about a 4 deg. swing. So i'm going to get some fans to point at the water.