Poor water circulation?

[HappyHooligan]

90g FOWLER lightly stocked at the moment. I have some rusty, cyano looking stuff on the sand. I have 2 270gph powersweep (which I'm not overly impressed with) PH's sitting at the top of the tank on both sides, aiming down as best I can.
Flow looks okay towards the bottom but am wondering if a better PH would make a difference.

 

[David S]

How old is the tank,it sounds more like diatoms,they will dissapear as quickly as they appeared.cyano is more like a jelly texture,can be caused by phosphates and nitrates and lights.what are you topping off with?

 

[HappyHooligan]

How old is the tank,it sounds more like diatoms,they will dissapear as quickly as they appeared.cyano is more like a jelly texture,can be caused by phosphates and nitrates and lights.what are you topping off with?

oh yeah, forgot about Diatoms. Tank is a little under 2 years old.

 

[David S]

does it brush off easily?