Oregon newts, as with other species, produce very toxic skin secretions that can and almost definitely will kill any other newt placed in the same tank.
a few years ago I had my pair of granulosas in a tub. When I took them out and gave them a new tank, I used the same tub later on to temporarily house three of my biggest spotted salamanders. Well, after a couple of hours of being in the tub (which I rinsed, but apparently not enough) two of them were dead and the remaining one was convulsing in the corner. I learned from that mistake.
Now when I change species in the tubs I usually throw scalding hot saline solution and scrub entirely.
