If it is a hillstream loach, it does not eat algae, and the warm, relatively calm waters that shell dwellers thrive in is quite the opposite of the cool, fast running, highly-oxygenated waters that the loach needs to thrive.
If it is a Hillstream Loach, I had one of these guys about four years ago. But sadly my little guy died a couple weeks after I got him. They like cooler temps and faster flowing water. These guys have also been called Butterfly Fish. Mine liked to stay on the glass walls all the time. I also heard they like smooth surfaces.
I've just Googled Hong Kong Pleco and every site says its a Hillstream Loach. Have a look at Google images and see if you can locate a picture of it there