I agree with TrickyD119 on the plecos. They just get way too big for a 10 gal, even the smaller types like the rubberlips etc.
IMO I think 1 or 2 Ottos would be okay for your setup, since you only have 2 balloon mollies in there right now.
In addition to the algea thats in your tank, you will need to feed other things like algea wafers and cucumber/zucchini like TrickyD said, so they get a balanced diet.