You could always put the newts in there and whatever else survives with it. Not to sound cruel but that is how I have seen many tanks setup. Put what is wanted in it and make several educated choices and see if they survive with the newt. But obviously don't put something in there that will harm the newt (ie goldfish or oscars). When I setup my aquarium I had some small angels and a pleco, well they grew up and were slightly aggerssive. So I housed guppies (which freely reproduce, and supply a constant nutritiuos food supply). They survive and many have outgrown the angel fish's mouth. Through trial and error I have found many fish who live with them and unfortunately many who don't. You may want to consider: guppies shrimp pleco betta oto cats. Who knows it may pay to get a little daring and put a larger fish in there (guaramis) or something. Look at africa, lions hyenas leopards elephants cheetahs large snakes and alligators all live together and none of them manage to be each others food source but are all highly aggressive/territorial. Keep them all fed properly and they will get along. Again my suggestion is trial and error, you will be surpised what will live together in harmony.
