What is going on??

[Sylvester]

Hi
Why does this cyano,red algae only grow here in the corner. The rest of the tank is white but this annoying stuff likes to grow on the sand bed,and behind the rock.
Any suggestions?

 

[Hydrored]

Vacuumed it up and get some more flow there. I have a spot in the back right corner of my tank that always has a dusting of it. Never goes away unless I completely change the flow in the tank, doesn’t bother me so I leave it be and vacuum during maintenance

 

[Sylvester]

Really eh. I guess that is my next attack
Thank you