ID please - Cyano or Diatom

How to check if this is diatom or cyano? if its diatom, I guess I no need to worry it will go off, but cyano will be concern?

It's kinda brown and only on sand.

 

Looks like diatoms to me. How long has your tank been set up and what is your water source?

 

previous owner had it for 5 years and I have it for 9 months. It all started when CC replaced with cheap silica play sand. I thought silica might be issue and replaced play sand with caribsea aragonite sand week back. Pictures I posted taken with play sand, now with aragonite sand nothing like that, but I noticed today thin layer being formed. RO/DI water change around 10 gallon every 2 weeks.

so if its diatom, it will go away on its own? sand layer becomes white again? apologies if its dumb question

 

If it is diatoms, it will go away on its own. I would think that they could feeding on left over silicates from the play sand. I have used play sand with no issues though. I just made sure I rinsed it really good prior to adding it to the tank.

 

Pretty much any new substrate will have silicates in it. Silicates = diatoms. Nothing to worry about, give it a week or two and it will be gone on its own.

There are CUC members that feast on diatoms too.

 

Honestly I spend hours rinsing play sand but whatever you rinse silicates won't go away only dust.

 

Even Caribsea aramonite aragamax has little silicates? they claim it's silicate free. When it goes away, do I get white color on sand again? I am afraid if it leaves brownish sand

I had nice CUC until all my hermits killed snails, ordered some nerite snails from reefcleaners today

 

You will be good, it will go away as if it was never there.

 

Well, you really need a microscope to tell the difference between the two, but since we all like to play the id this game, I'll go with diatoms...

 

You made me feel better !! thanks