Brown algae causes

I have some brown algae issues in a well established tank. I do keep on top of it by using a scrubber( i keep african cichlids and they are generally peaceful but do not like plecos). However, I'm wondering what the causes of brown algae are, and are there any other common algae eaters that work well with african cichlids to keep on top of the problem, or would it be better to buy a pleco thats bigger than my 2 1/2 inch cichlids. A chinese algae eater possibly?:-/

 

How often do you change your filter media? Vacuum the substrate? Do water changes?
What type lighting do you have? How long do you run it daily? Does your tank receive sunlight through a window?

"An ounce of prevention is worth a pound of cure"... An algae eater is just a band-aid.

 

I have 2 cartridges so i replace them every 3 weeks alternating between the two. I vaccuum the substrate every water change every 2-3 weeks. I believe the problem is light. I do run the light quite a long time and it receives some sunlight, not directly though. I will cut back on the light. Thank you!