HELP: Brown stuff on inside of tank?

OK, this is in our third tank and ive only had all three running for about 2 to 3 months. Ive had normal growths of green algae in the other two, but maintenence and snails and shrimps keep it all under control.

However, in our tank upstairs there was a small (2cm) spot of brown on the inside of the front glass last week. I wiped it off thinking that it was just dirt.

However, there are several more growing near the same spot now so does anyone know what this is and how to deal with it??

Algae or cyanobacteria. For lots of info, go to http://www.thekrib.com/Plants/Algae/

My daughter's 10 gallon started getting a ton of brown algae on the artificial plants. Got 2 Otocinclus Catfish and within 24 hours ALL traces of brown anything were gone! Otos do a terrific job of housecleaning.

Sometimes I get that in one of our tanks, it seems like a brown algae that grows where the light doesnt shine well. It has never seemed to be of any harm in my tank. I just wipe it off when i clean the tank.

-Dundee sama