Round brown spots on my substrate

Hey Guys and Gals,

I have recently setup a 90-gal tank with aragonite(fine grain) sand and just finished my cycling. There's nothing in the tank except sand and water. I have my live rock curing in a tub, it's not ready to put into tank yet. But anyway I have started to notice that something brown and spotty is starting to build or grow on the sand. It's like a spot with a darker brown spot in the center of the spot, hard to explain. It's looks like something was growing on a particular grain of sand and started to expand out, biggest I've seen is less than Dime size. Don't know what this is, could be diatoms, any help in identifying is appreciated. By the way my water parameters are normal, ammonia, nitrite, and nitrate.

 

check for deadspots ie water flow ..

 

Actually these spots are located in areas where water flow is good. I don't have anything in the tank. So water flow is not being obstructed.

 

weel okay try running some carbon .. hows your p04 levels??

 

I have a sump with Carbon already running with the Tank,... it's been 4 days since I put carbon in. Po4 is 0.

 

are you running lights too long is it too much lighting and yes i know its empty

 

is it slimy looking?

 

Sorry mattgeezer no insult intended, only NO lights 80 watts. not slimy just brown Mario8402.

 

lighting spectrum too low i too only have no lights at moment so i get heaps of algae ...so its your lights get some t5s or something no insult taken bro

 

How do I insert a pic. I have a pic of the tank sand.