Only get an algae eating fish if you like the look of plecos, garras and the like. Please don't get them just to eat algae.
However, to answer your question we need some very basic info first:
Tank size?
Ph level?
Temperature?
Tankmates?
Planted heavily or not?
If planted with highly edible plants such as Elodia Densa and Amazon Swords or highly unpalatable plants such as java fern and anubias?
Filtration?
There is also the question of nuisance algae or normal algae? If it's very problematic and rampant then there is a root cause that needs to be addressed if it is not rampant (all over your glass withing days of wiping it all off).
Is it just regular algae, such as on slow growing plant leaves (anubias sp) or spots occurring here and there?