I also think its a Sucking Loach or Chinese Algae Eater. I have two of those in my planted tank, they love algae but as they get older the only eat brown algae en get agressive, but more to its own kind or anything that look sorta like it.
Some people say they suck the slime coat of slow swimming fish, bet never notice it. Mine is four years old and still eating green algae from the leaves of my swords, and are slow growing fish, only 3".
I would not recommend them for a beginner or a small tank <20G, and not on its own, as long they chase each other the rest of the tank is left alone