Brown algae-diatoms are very normal in new tanks as the bacteria colony is not efficient enough and there are always traces of ammonia left, although not detectable on most tests.
If you are suffering with brown algae in an established old tank, then the tank maybe overstocked, or overfed, or just doesn't have an adequate filtration for the size of the tank and bioload, causing ammonia issues. Lack of circulation around the tank also doesn't help diatoms.
But then again in every tank there's a bit of algae and it's not necessarily a bad thing as it provides more natural food source for the fish. If you want a snail to help with cleaning while you are dealing with the issue, get nerite snails. They don't multiply in freshwater and will eat the diatoms too pretty efficiently.