What is this? Cyanobacteria? Diatoms?

[zatchyvsalt]

I have a 75 gallon tank and it has been well established for about 1.5 years. I recently added some already cycled rock to by tank that was from an already established tank at my LGS. My tank is now covered with this brown material all over the rocks and sand bed. It also coats to the glass almost like a film. I was thinking cyano but not sure. It also goes away at night when lights are out and sort of dies off only to reappear during the day.

Can anyone help me identify this? Maybe the rock caused a diatom bloom? I understand if it is diatoms just to wait it out until it eats all of its food source.

Any info will be helpful.

 

[shakacuz]

dino's. especially if they "go away" during lights out. could be a combination of both, though.

what are your water parameters? what CUC do you have in there?