HELP! Grape Caulerpa turning white!!!

[redtang]

I have a newly set up fuge, 20 gal. rubbermaid with 4" livesand, 4 little pieces of LR, and about 1/4 lb. Grape caulerpa in the fuge. I have two lights, one 20 watt actinic that is on 24/7, and one 150 watt home depot indoor plant light, on 12 hrs. a day. The last 2 days I have come home, and a little more of the caulerpa has turned white. I trim it off, but why is this happening?

 

[redtang]

My tests are good, with the exception nitrates, consistantly 40 ppm. Thats the reason for the fuge.

 

[redtang]

What about switching the actinic wit a 20 watt general electric cool white? Also what do you think about using the 150 watt indoor house plant?