I have heard cynops species are easy, and that plurodeles watl are very easy. But from personal experience, if you keep triturus karelinii well fed and the temperature changes a couple of degrees for a month or two they will breed without any other work. (I had mine in a cool basement for a month and a half during a hot summer and they bred in the fall, and then last winter the temperature just naturally got a few degrees colder because we try to save money on the gas bills and they went into breeding dress, but I seperated them because I didn't want to be swamped with larvae!) So i don't know about easest, but it certainly is easy to breed them. I would also reccomend them because they are a larger species and I have found it is always easier to feed larger species as larvae and juvenlies. But plurodeles watl is even larger, except I have no experience with them, so I cannot give you advice as far as they are concerned.