I've got a large rhino pleco and a king tiger in with my motoros. Neither one sucks on my rays. The rhino is about 9-10inches and the king tiger is 6-7inches. But I also have a large piece of dogwood where the king tiger stays. The rhino is always all over the tank. I haven't had an algae problem in my big tank for over two years. I also had a leopard pleco in with the rays but moved it to do some algae work in my 55.
I don't know that there are specific plecos that are guaranteed not to try to suck on your rays...whatever type of pleco you choose, you have to watch closely for a while until you're sure your rays are safe.
I don't know that there are specific plecos that are guaranteed not to try to suck on your rays...whatever type of pleco you choose, you have to watch closely for a while until you're sure your rays are safe.