I agree with Hydrophyte that fish are probably the best bet. But newts are my hobby, so I can give you some advice with those.
Salamanders live on land, so they would not be suitable. However, there are a few fully aquatic newts that would do fine in a riparium. All of them will need cooler temps 60F - low 70F. There are considerations for each species, which I've tried to list below
Hypselotriton orientalis (Chinese firebelly): these are the little black newts with the red bellies often sold cheaply at large petstores. Always wild caught, they arrive in poor condition and often do badly. You can get them captive bred, though. Similar species are the Gold dust newt, sword tail newt, (all Cynops species) etc. These others are almost always available as captive bred. They also all stay pretty small, are nice looking, and are non-aggressive.
Notophthalmus viridescens (Eastern newt): the little green newts sold cheaply in petstores. Never available captive bred. I have these and I love them, but I can't recommend them because the wild caught newts do so badly.
Pleurodeles waltl (Spanish ribbed newt): Big and personable, and always available captive bred. These guys also do well at slightly higher temps. They make great beginner newts.
There are others that do fine fully aquatic, but these are the most commonly seen. All of these will eat live earthworms, blackworms, shrimp, or frozen bloodworms (those little cubes sold in petstores).
ETA: Forgot to mention that all of these also require a lid on the tank - either mesh or glass - because they can all climb. Same for any frog you might put in there.