I think mine are Otocinclus Vestitus, and the ones you're referring to are Otocinclus Affinis. Mine aren't golden in coloration like the latters description. Mine are brown with a dark brown mid-section running from the head-tail. I don't know if O.Affinis looks the same?
The most I've ever seen my Oto's eat are cucumber slices, live foods and algae, but have never seen them eat my plants. I wonder does it matter what type of plants you may have in your tank, that may become food for them?
I have 3x 0.Vesititus's and they get on well with each other, because this number appears to suit my tank size. As they're semi-aggressive to each other I think you'll need a slightly bigger tank if you're thinking of getting 6 of them.