Depending on the size of your tank you might want to look for SIAMESE Algae eaters (SAE
). They are often sold from petsmart for a couple bucks. They can get 6ish inches so NOT for a small tank.
Otos are great, they like being in groups of a few on up, figure about half will likely die and you might not find the body to return it for the refund/exchange. They are more delicate, due to the hard time of wild capture and traveling so much. As mentioned above they are pretty hardy once acclimated to your tank. Though they don't like poor water quality.
Make sure to feed them little amounts/pieces of algae wafers unless your tank is got a supply of algae. You can also grow algae rocks for them. Wild caught are used to eating naturally and not from pellets.
Don't forget to quarantine.