Bristle nose, bull dog or clown plecos are great for that size tank but TBH if your only motivation is to get rid of diatoms(the brown algae) I wouldn't bother. They are ok algae eaters but as they get larger they slow down on it and they always need other options to fulfill their dietary need. Diatoms are fed mostly by silicates in your water, eventually they will go away on their own as time passes. They are different than the usual "green algae" you see in that they don't really get caused by light.
Plecos are great little guys for a tank but the idea of getting them as a clean up crew or simply to help with algae isn't a great one. They will make a good member to your tank but plecos are messy fish as well, pretty high bio load. So just weigh why you want one. If it's only for algae or clean up then I would pass it up and just wipe it off until it clears up. If you want one for the great addition to your tank than the Bull dog, clown and bristle nose are great options for plecos. There are other cats that are really neat too. Like the striped or spotted rapheal cat. They are one of the neatest looking cats I think I've seen next to the more exotic plecos.