Is it alright to put a Pleco in a goldfish tank?

I added a Pleco to my 10 gallon goldfish tank yesterday and everything seemed fine, but today I've noticed that it is swimming around an unusual amount for Pleco's and has been latching onto the side of my large goldfish (which are only about 4 inches) and seems to be following them around. Is it just getting adjusted to the tank or is it possible that it is going to hurt my goldfish?

Is that an algea eater? They won't hurt your other fish the are whatever the opposite of aggresive is...docile.