Ugly brownish algae??

I have this brown algae on certain areas in my tank! They are little patched and theres about 3-4 patches heres a pic of one of them at the top of the tank. What specifically is it and how can i get rid of this?? it toward the back area of that rock shown. I clean it off and it seems to just come back

 

Diatoms

 

Or Cyano, how long has your set up been running?

 

Its been running about 8-9 months

 

Either way, the amount you have is not only completely harmless, but beneficial as well, as it is feeding on nutrients/contaminants that would otherwise stress your tank far more than an algae bloom.

If your tank is fairly new (less than a year old), it may just be a 'cycle' and will disappear on it's own. If it continues to spread, however, you only need to reduce nutrient import and/or improve your maintenance regimen to get rid of it.

 

that wouldnt harm much but rather it would benefit your tank in taking all contaminants.
however if it goes on increasing then you will have to take special care of your tank and its maintainence