well pending your decor, keep it 'root' filled, suggestion use drift wood... pleco's are naturally found in highly rooted areas.
if it's adonis pleco, they can get up to 40 inches (takes a long time) ... pending the tank size.
they are peaceful and can be kept with cichlids and large characins (Anostomids, Hatchet Fish, Metynnis, Pencil Fish, Serrasalmus, Tetras)
As for with
Goldfish, I'm unsure never tried, I'm not a huge fan of
Goldfish lol.
What kind of things do you look for in fish.... color, easy to keep, etc?