My Pleco Wont Clean My Tank?

I have had my baby Pleco for about a week now. Currently, it's in a growing out tank, so its not huge. I have both plastic and live plants plus two ornaments for my fish to hide. My pleco is in the company of 5 small goldfish. I have a build up of algae on the glass, and my Pleco is nowhere insight. I have already blocked off it's usual hiding place under the filter as I dont want it swimming up there and getting stuck. So it has a bridge and a log to hide in. But all it does is hide. I know they prefer to do come out at night, but how do I know its eating??