Most limnivores will not touch higher plants; at least those still fresh and living. You generally won't have to worry about them eating your plants, though you can never be too sure.
The large common may cause problems, but probably not. Try it out for a few days and see how goes. The main concern I'd have would be food competition,as a large pterygoplichthys will always get to the food first.
The large common may cause problems, but probably not. Try it out for a few days and see how goes. The main concern I'd have would be food competition,as a large pterygoplichthys will always get to the food first.