Tank Setup

Most salamanders, being native to temperate climates, don't require heaters like tropical fish and reptiles do. They thrive at room temperature -- about 70F or 20C. They all need water and most need some land. Water chemistry is not as critical as for fish, because newts breathe air, but you should keep track of things like pH and ammonia so they don't get out of control.

small newts

Fire-bellies, cresteds, california/oregon newts, and redspotted newts should be kept in a tank that has both land and water areas; the water area (even for just one salamander) should be at least four inches deep. There should be enough land that all of the salamanders in the tank can walk around on it. The best way to do this is to use aquarium sealant to put a divider in the tank; fill one half with water and the other with stones, commercial reptile substrate, or other appropriate materials. I don't recommend piling up gravel to make the land area; this takes away too much swimming space. You can also use an island or shelf of some sort (pet stores sometimes sell these). Just make sure that the newt has plenty of space to swim and to walk around, even if he seems to prefer water to land (or vice-versa). A filter may be a good idea for the water portion. A five-gallon tank can house 2 or 3 newts if it's set up properly.

axolotls and larval tigers

These guys are completely aquatic, and require an aquarium filled to the top, though you should keep a close watch on them and provide them with some solid ground when they're ready (when they almost look like adults). Delicate filter systems are usually out of place; "waterdogs" are messy enough to require complete water changes (strip the tank and scrub everything) and they don't care much about water chemistry. Clean the tank with baking soda, which is not toxic like soap, but does a good job of cleaning. Each of these guys should have at least 2.5 gallons of water apiece -- meaning no more than two in a 5-gallon, and even that is pushing it.

terrestrial salamanders

Terrestrial salamanders need water too. Amphibians don't drink; they get their water by soaking it through their skin, so they need a place to soak. For the substrate, use one of the mulchlike commercial substrates, or something of the sort (gravel rarely works well, and astroturf is too rough for their thin skin) and sink a large bowl into the substrate to make a sort of inground pool. Give a single tiger his own 5 or 10-gallon. Most people don't give these guys enough space.