If you are looking for an algae eliminator, a magnet scraper and a horsehair brush are more effective than any loricariidae will ever be. The truth is, if you provide your fish with a sufficiently satisfying diet, 9 times out of ten they will not TOUCH algae, which tends to be a last source of sustenance, even for herbivorous species--this on top of the fact that only a limited range of algal growth (the brown, diat stuff found only in very mismanaged or very new aquaria) which should be nearly absent in well kept displays.
Neither royals nor green phantoms of either species are heavy algae eaters.