What is this on my sand?

[Lazys Coral House]

I have had this issue with my sand for quite some time now, maybe a year. I can't remember the last time it was nice and white looking. When the lights come on it is fairly white with a little brown. By the end of the light cycle it is really brown. I bought about a year ago 3 cucumbers and a couple months back 6 conchs. None of that helped. These diatoms or algae grows and disappears every day. Anyone else have experience with it? Here is a picture of it.

 

[Mr. E Wrasse]

I say diatoms. If you have your lights on too long that will do it. Also over feeding

 

[Lazys Coral House]

My lights run 5pm to 11pm. They are two 400w 20k. I don't feed much and my phosphates on hannah meter are .03 nitrates are about 2-5. That is why I don't understand why the issue. It is strange and how it disappears every day and grows back kind of weird. Is that indicative of diatoms? Sand bed is about 2" and I clean it about every other month by siphon.

 

[mike007]

Looks like corraline to me. No worries. If it bothers you vacumn it when you do water change. Tank looks great.

 

[Mr. E Wrasse]

My lights run 5pm to 11pm. They are two 400w 20k. I don't feed much and my phosphates on hannah meter are .03 nitrates are about 2-5. That is why I don't understand why the issue. It is strange and how it disappears every day and grows back kind of weird. Is that indicative of diatoms? Sand bed is about 2" and I clean it about every other month by siphon.

Hmm that is odd. I had the same problem, which started during the summer when we get more sun light down here, I ran my lights 2 hours less and it went away just like that. Not sure what it could be then

 

[Lazys Coral House]

Someone mentioned on my local forum that it my be dinoflagellates. I may try some h2o2 dosing for a couple days to see if it helps