I could be wrong, but personally, I wouldn't put a pleco in a 10 gallon task. It seems a bit small for one of them to me. And I am pretty sure they don't eat brown algae. Maybe get some mts to help with algae, but not sure if they eat the brown stuff either.
What a "pleco" will eat is determined by the species, but for the most part they eat green algae, There are some ancistrus species that a pair would do okay in a ten gallon but the common pleco is not appropriate to that size tank.
Most of the Plecos regularly found in pet stores need much more than 10 gallons. If brown algae is the issue get a Nerite Snail. Nerite Snail are more efficent algae eaters than any fish in my opinion. Plecos will not eat strictly algae. You might also want to consider Amano Shrimp, they are great algae eaters and have big personalities for shrimp!