They are doing a fine job on algae. Much better than Ancistrus that seems to only go over wood. Panda's go over plant leaves something Ancistrus hasn't done. Panda's seem to ignore wood..I would guess its not needed unlike ALL the Pleco's of the world. Panda's are more Labeo like..but much,much, better than them on algae.
Plus Panda's do all this in the day where you can see them.
Try and get a pic..but they are 2" or less. Chances of getting a sharp picture is low with my camera!