Yes P nigroliniatus (Royal pleco) is breedable. Any one living north of Rockhampton would be advised to try them.
The do get a bit big though. The breeding fish that I saw were housed in a 10 foot x 5 foot x 3 foot deep out door concrete pond. There were five fish, all over two foot and the biggest (presumed to be the only male) was in excess of 2'6". The pond was stacked with sunken logs, no aeration or filtration, just an overflow standpipe. I have no idea what the water was like. Water changes happened when it rained or if the weather was dry and the level got too low, the pond was topped up and let overflow with water pumped from a creek.
The pond also had three lengths of old clay sewage pipe about 4 foot long and six inches in diameter and because the baby fish were first seen all over one of these pipes the breeder thought that the eggs must have been laid in this.
The diet??? now get this guys,,,, unreal !!!! Chinese cabbage ( which he used to grow) and chook pellets !!!! and what ever else grew naturally in the pond.
When I saw them, the babies just looked like little inch long, dark brown/black bristle nose, no pattern at all. This was some years ago, so where did all those little panaques go??? And any subsequent spawnings ???
Sort of knowing the guy, they probably all ended up back in Germany or the USA.
He also had the only H zebra, and fry, that I have ever seen live in the flesh.
Alan