Brown algae?

After finally getting of my problematic green murky water situation and now
enjoying a clear tank, I notice that the walls of the tank are getting a
brown film. I used an algae "scrubber" to clean down the sides, but the
brown returned quickly. Since switching to an Aqua Clear three way filter
and only putting a capful of "Cycle" in the water, I don't want to start
throwing all kinds of products in the water unless I have to.

Any input greatly appreciated.

Tispe