Brown Spots On Tank Walls?

[Sanjay]

Hi all!!
I have noticed recently there are brown spots appearing on the walls in my tank. I am assuming this is algae. I am doing a 25% water change weekly and all the readings check out spot on. The lights are on for 4-6 hours daily.
Is there anything i can do to prevent this??

 

[Smelliot]

Probably just a case of diatoms, besides reducing/cutting off light completely having live plants could help you out. Diatoms are caused from excess nitrates in the tank. I'd personally just scrub it off do a water change then put the tank into darkness for awhile a CUC (clean up crew) would help you out too if you chucked a bristlenosed pleco in there for example you'd notice it vanish within days.

 

[paradiddle]

I have the same issue too, but thats because i have no live plants and my tap water is high in nitrates, my cichlids would eat plants and i cant do much about my tap water! 
So... my solution is Seachems Purigen, it controls organic waste material, give it a read up, should help you too,

 

[Sanjay]

Thanks for the advice!!

 

[Plecc]

Is the tank close to any natural sources of light, windows, doors etc?