I had a problem with green algae so I installed a new air pump... lots and lots of air.
However, now it seems the green algae has turned brown. Is this a different type of algae or just dead green algae? It feels slimy and wipes off pretty easily and you can see brown particles on the paper towel after wiping. Maybe it isn't algae? Not sure....
I'm just wondering if I need to clean it off the sides and bottom or just leave it.
If there is enough algae to cloud the water, then you want to get as much of it filtered out of the water as you can (letting some algae decompose in your media beds can help inhibit future algae blooms.) If it is just a thin film on the surface, I wouldn't worry about it.