Brown (Diatom) Algae

[bpachal]

Hi everyone.
I have always come to Canreef as a non member but I have a brown algae problem that is kicking my but.

I have a 160gal tank + 30gal sump. As of now there are no fish in it as I have moved them to another tank. I did this because I set up a reef structure using some non cured pieces of live rock in addition to my cured pieces. I kept the existing substrate and got rid of most of the brown algae.

The idea was to eliminate the excess nitrates in hopes to starve this stuff. But right now it seems to be taking over again.

Ammonia is at 0.1
Nitrite is 0
Nitrate is 0
Phosphate is 0
Calcium is 340 (working on it)
Kh is 170
Light cycle is 9am-730-pm (4x 6foot t5 HO's)
Uv sterilizer is running

I did each test twice to make sure. Admittedly it is not taking over as fast as it was but its increasing not decreasing. Again just live rock, substrate no fish until I am sure ammonia will not spike due to uncured live rock. Any suggestions anyone?

Also- I use only RO water for changes with TDS of about 11ppm

Thanks everyone.