If its a new tank or a tank with new plants in it, its probably a diatom bloom, a sort of fine hair or fuzz, and yes its brown and will get everywhere, if it is a diatom bloom they can last for a few weeks or they can last for ages, months, there is no real way of telling, if it is a diatom bloom otocinclus (or ottos) will think its christmas and new year all in one, they love that stuff and will clean your tank up, and they are a great little fish as well.
If you think it is a diatom bloom id get 2 ottos for a 10 gallon, they dont like to be alone so a pair would be better, sometimes they can be hard to aclimatise but personally i havent had those problems with them, i introduced 6 ottos to my 40 US gallon tank and in one week the tank was super clean ( and believe me i had a major diatom bloom ) but dont expect miracles overnight, give them a little while.
If you were going to buy them i would read up on them, but they are a great little fish, you wont regret buying them, they are great little workers allways looking for more brown stuff to gobble up.