It depends on your tank size, for smaller tanks, Otocinclus Affinis are very good algae eaters, the rid my tank of brown algaein a couple days. I have two in my 10gal.
In bigger tanks, Look into different ypes of Plecostamos. They get bigger and will eat more algae, but poop a lot and add to the bioload.
Get different people's opinions on the best Pleco. I have a Clown Pleco in my 20gal. He doesnt come out much during the day, But I dont see any Green hair algae and almost no Brown algae.
Otos do an amazing job of cleaning up, and mine never bother any of the other fish (I use them in a tank with fry). They're quiet, cute, industrious little guys. As a bonus, they add next to nothing to the bio-load (compared to a large 'pleco') since they stay under 2". I keep 3 in my 45g and there's hardly a trace of algae.
They don't seem too fond of the hair algae that I've got in my tank, but they will absolutely demolish any green algae. They'll take on the hair algae after they've finished off everything else, though. They're tiny, but those little buggers can eat There's my vote for Otos
this seems to be a very hard to answer question. everyone has different results and I think this is a result of all the different types of algae. I have otos in several tanks and they do a descent job over small areas but if you have a larger tank or lots of algae, they don't seem to do much good (at least in my experiences). I had a couple tanks covered in brown algae and the otos weren't working in one tank so I bought a bristlenose pleco for a different tank and he cleaned the whole tank in a couple days. Drawbacks are they get around 4-5 inches, produce a lot of waste and don't seem to have an apetite for green algae of any type. I have since moved him to a 65 gallon planted tank I started having brown algae problems with and was curious as to whether it would eat or uproot plants or not. I was amazed as to the delicacy it shows even to the softest plants. they also seem to clean in spurts. it went for 2-3 days with only minor progress and then one night it cleaned the whole tank like a scrubber. The only tanks I have that are truly clean of green and brown algae (except hair algae) are the ones with standard pleco's. unfortunately we all know how large these get and how much waste they produce. chinese algae eaters have proven aggressive in more than one case so I would not recommend them. I've heard siamese algae eaters are much better but have never owned one so I can't comment on my own. Well, if I havn't confused you enough already, this might give you some ideas of what to expect. Kyle
I really like my bristlenose, but he doesn't clean algae worth a squat. I just wanted to throw that in.
Actually, to be fair, it's kind of like snakeskinner's experience. He'll not clean for a while, and then he'll clean the entire tank. He poops a lot, too.
There's my vote for Otos 
