Truly baffled

I had been having issues with diatoms. I switched from distilled to ro water and for weeks my tank looked great. Diatoms finally were gone.
I did a water change sunday and voila yesterday my tank had an ugly dusting of diatoms on my sandbed.

I just don't get it. The only thing added was a surface skimmer which I cleaned in vinegar water and air dried before it went in my tank.

It makes no sense. I use io salt, ro water, feed 1x a day, I add a tiny bit of zooplankton to my tank.

I really am baffled

 

How long ago was the skimmer added?
I am more than willing to guess that is the culprit. The good thing is the diatoms shouldn't last long

 

Sounds more like brown algae/cyano.Take a picture of it.

 

I added the surface skimmer the same day as my water change.

I tried taking a pic but its not at its worse yet, as the day goes on it will get worse...light.

Never ever had this issue before in any tank. I'm so damn good about maintenance.
I'll post another pic around 7

Its not red or slimy, no bubbles in it.

Golden to dark brown, not like hair algae but it looks kinda like lint sitting on the gravel

 

Its worse now at 8pm

 

My guess is the zooplancton- sometimes this stuff creeps up and it's immpossible to figure out,
I've even read that WC's can cause it! Hang in there.

 

Just looked at your pics,
Don't sweat the small stuff, take a stick/rod and stirr the top a bit.
Looks minimal in those pics, just my 3cents.
I've had GOBBS of GHA- only on my thin sand bed for months now- I just siphoned alot more of it out as most of it is dying now- Yea!
YOur bed looks fine to me

 

Fwiw cyano can be red,green,brown, or even black and doesn't always have bubbles in it. I am with Todd on this.☺

 

I know its not too bad but it makes you g
think wtf! It was just gone.