Lots of different fish eat lots of different algae. For the stuff on the glass, Bristlenosed plecos (regular or albino) stay under 5", Bulldog Plecos mostly stay under 5" (the ones from PetSmart are one of the smaller species), and Pitbull Plecos stay around 2". Ottos are also great glass cleaners, but can be a little delicate, ans sometimes will ONLY eat algae - one per 10 gallons of tak will make it sparkle.
For hair and brush algae, shrimp are great. Amanos do get an inch and a half or maybe a little more (I have 6 in two tanks, from just under 1" to just over 1.5") They seem to do an OK job, but I really don't have enough for full algae control (5 per 20 gallons or even 10 would probably do better).
Mollies, Sword tails, and American Flag fish (sometimes incorrectly called Florida Flag fish) all do a good job on green thread algae. Unfortunatley, they are all hard water fish.
Siamese Algae Eaters (SAEs) get up to 6" log, but are the only fish know to eat Black Brush Algae, and they eat the other kinds of algae too. False SAEs look very much like SAEs (there are differences) also eat some algae, but not quite as well. Chinese Algae Eaters only eat algae when young. As they age, they get aggressive and carnivourous. Don't buy them unless you are planning on setting up a species tank. Here's
a rundown of the various look-like Southeast Asian algae eaters.
Butterfly Plecos, aka Hong Kong Plecos, accurately called Hillstream Loaches also eat algae, but they prefer cool, well oxygenated water and a strong current. They're really only suited to a subtropical river tank.
In a 55, I'd go with (In fact, I have gone with) a pair or trio of bristlenosed plecos and/or three SAEs. If it were a long established tank, I might get 5 to 7 Ottos.