>>>i have to ask, but do you really think that java moss and ferns will be suited for a tank with only 2-3 inches of water, i would think they would spread across the surface and take up a lot of the space in the water area, i suggested tropicals because i use them in my firebelly tank and give the tank a good look, provide shaded areas, areas to climb and hide, and don't take up much of the water space in the process. as for climbing out, firebellys are the master of this and i have never had one escape as long as the screen was on and in place. i think that the javas would work well, but only if the water level is raised to at least 4 inches
Yes. Not only do I think it will be suited for a tank with only 2-3 inches, I know it will work. I have several tanks that are set up like this, including ones for T. cristatus, C. pyrroghaster, S. marginatus, Siren intermedia, and Mesotriton alpestris apuanus. The lack of "open space" in the water really isn't much of a concern to the animals - only to the viewer (assuming he or she cannot see the animals, which is not the case with my animals).
Tropicals, as you suggested, are fine, however the problem lies in the name: tropicals. Most caudates prefer to be kept at temperatures cooler than what most tropical plants prefer. Granted, C. pyrroghaster can tolerate warmer temperatures better than many caudates. Pothos, in my opinion, is probably the only species that I would use in an aquarium, myself. Here are some specs that might present difficulties with your other plant options:
Spathiphyllum - tropical plant. While tolerant of low-light, virtually all varieties that are commonly available get much too large for most aquaria. Also, despite people selling them as fully aquatic plants, they are not.
Arrow arum - Unfortunately you did not specify a specific genus, but many species of arrow arum require a period of winter dormancy, as well as requiring higher light conditions. Also, these species tend to get much too tall for the average aquarium - upwards of 2' or most in most species. A much better choice for an outdoor pond than an aquarium.
Pickerel Rush - (Pontederia cordata). A plant that is tolerant of a wide variety of lighting, however, it too often gets much too large for the average aquarium - 2 feet or more. Again, much better suited to an outdoor pond.
Again, in my experience the best, most long-lived and successful combination of plants for most newt species are java moss and duckweed. It does not require deep water (honestly, 2" is just fine. If you want more room, you can easily thin the java fern), is tolerant of cool temps, as well as provide many other benefits (water quality, cover, etc).
Hope that helps,
~Mike