I got a little newt that is similar to a firebelly newt. Doing really well. Very easy to take care of. Lives mostly in water but walks around the terrarium from time to time. The water is a shallow pool 23cm/9inch in diameter and 3-4cm deep. Have water plants in it from aquarium store.
Newt eats just about any fresh food and always takes food under water. Anything from a fish market, sliced into small thin strips. Slow or squashed insects. What he really likes best are live earthworms from my garden, which I am able to dig up in winter on a warm day. I went away for a month and fattened him/her up before I left. Was very healthy when I got home. The terrarium lights were on a timer and a friend watered the plants.
I am advised to change the water in the pool, as the newt relieves himself in that water and over time it might build up toxins. I only add rainwater or distilled water. Always leave some old water and dirt on the bottom so bacteria get started quickly in the new water. A really clean bowl lacks ammonia-converting bacteria.
Because the newt is a slow animal, he does not break plants and make a mess of the terrarium.
Here is a link that might be useful: