Debi,
I went back and re-read some of your posts on your recent 55 to 135 conversion.
You guys used the established sand from the 55, and maybe topped it off with some new sand ?
Increased lighting for sure.
DI water and I assume Instant Ocean ?
Added a new large piece of live rock.
From your second picture - it's clear that the diatoms skeletons settled on the sandbed in areas that receive direct lighting from above. Around the edges of the corals, and overhangs of live rock - the sandbed is still very white.
So I would say that lighting is playing a major factor in it's growth.
But we already knew that .. right.
Is there any diatoms on your corals or live rock ?? It doesn't look so to me.
How about the glass ???
I also read where you've tried various different frehswater sources. Some store bought, some from LFS and now sounds like you are making your own DI ?
What DI unit are you using by the way ??
I know diatoms can be unsightly, and can make the tank look bad, but here's an interesting article you may find interesting.
It's a refreshing look at diatoms in our reef tanks, and goes into details that I was not aware of.
The article is written by Craig Bingman - and certainly shed some new light on diatom growth for me. It's kind of long ..... but I still think it's worth reading.
It's possible that the bloom is about done - and before too long - your sandbed will "look" better.
Sorry for asking so many questions.
Hang in there !
read me if you want to