Why is it that whenever someone on the forums asks about brown algae, our first response is to buy more animals? Pitufo, brown algae is not dangerous, is common to new tanks, and usually fades away over time. The easiest way to get rid of it in the meantime is -- as you've discovered -- to rub it off with your thumb. If it starts growing on the glass, use a razor blade or a magnetized scraper (they likely sell these at your LFS -- look for "Mag-Float") to get it off. It'll probably take a few minutes, twice a week, if that.
Otos are wonderful, but you have to consider whether they fit into your eventual stocking plan or not, whether you want to take care of this type of fish, etc. Unless you have a densely-planted tank, I wouldn't buy otos just to keep brown algae in check, because brown algae dies down as a tank is established, and it's so easy to take care of yourself.
That said, otos are compatible with your current tank residents if you are interested in getting them. Check out
http://www.otocinclus.com/ for information on otocinclus care.
I agree with happychem that snails are excellent tank residents -- they are too often maligned on the boards. Malaysian Trumpet Snails (MTS) are a good "starter" snail, and your LFS should give you some for free if they have them. Don't expect them to tackle your brown algae all on their own -- they'll make a dent in it, but won't eliminate it -- but they are beneficial for all the reasons that happychem mentioned. They're also valuable because they burrow through the gravel and help prevent anaerobic pockets from forming in your substrate.
HTH,
John