Diatom mystery

[Reeferrunner]

Ok so here's another "whats causing my diatoms question"... I have searched this forum up and down and learned a little about what Diatoms are and what they need to survive however I am stumped because to the best of my knowledge my tank does not have what they need.

So here is the situation... My tank completed its cycle at the end of July, so I know that I am basically right on schedule for a diatom bloom however it is going on week 2 and they are still dusting my sand and my rocks. Its not an overly aggressive outbreak but unsightly none the less. So I am hoping that someone can shed some light on what is causing this outbreak of diatoms and what I can do to get rid of it. Seems like I am already doing everything people recommend and its not working. Any ideas?

Tank Parameters:
36 gallons
ATO: RODI with Kalkwasser(1 tsp per gallon)
Water changes: 15% weekly
Lighting: Current orbit Marine IC pro Dual( 60 min ramp up and down full power 7 hours a day) Par on the sand is about 130
Caribsea Life Rock: 25lbs
Fish: 2 clowns, 1 Flame Angel(fed once a day hikari marine algea frozen or pellets)
CUC: 10 Astraea(eating diatoms off rocks not really on the sand), 10 ceriths, 10, Nasarius

Ph: 8.0
KH: 9
Nitrates: 0
Phostphates: .02
Calcium: 460
Temp: 77.5

 

[DirtMcGurt]

One thing I see is that you have zero nitrates. I'm definitely not an expert on diatoms and what they need but when my nitrates and phosphates fall out of balance, diatoms seem to appear. Try getting those nitrates up above 2ppm. Between 2 and 5 ppm seems to be a good range. Also, don't let either nitrates or phosphates hit zero. You tank needs a little of each.

 

[BeejReef]

7 hours of full spectrum is a bit longer than most.
Two weeks of diatoms isn't really out of the ordinary and I wouldn't be overly concerned about it. The rocks will continue to uglify until they're covered in pretty coraline.

You must be running pretty good filtration to get near 0 N and P!

Out of curiosity, do you have any corals? Why the kalkwasser on a brand new tank?