If you want to keep an accurate temperature measure leave that thermometer submerged in the water .
I would also stick a bit of matured bog wood in the tank,and the gravel is gonna be a pain in the butt to clean dude.
I would still recommend these as a species for you
Caudata Culture Species Entry - Tylototriton verrucosus
Well, I may be a little biased, but Tylototriton verrucosus are a good first newt to have.
Do you know what sort of temperature the water is as many newts and salamanders will prefer cooler water temperatures.