If you can only choose one and you've got green algae, I'd say go for a bristlenose. They're cute, stay fairly small, and they work hard. If you've got hair algae/brush algae, the SAEs are what you want. Once you remove what's already there, they'll take care of any new growth. Most other fish won't even touch the stuff. If the algae is brown (diatoms) you want otocinclus catfish - they'll gobble it up in no time, most other algae eaters don't bother with it.
