I have a pair of chinese fire bellied newt, cynops orientalis, (beware as labels of chines fire bellied, japanese fire bellied and paddle tailed newts are often mixed up in shops. make sure yours is cynops orientalis as the others grow larger and have differing requirements). They are very happy in a 45cm tank, sorry i cant remember the volume, and have lived their for three years without a single health incident. Very hardy and interesting animals i would highly recommend them.