Salamanders and newts have sensitive and porous skin and are very susceptible to changes in their environment. When setting up a tank for these species, try to emulating the natural habitat of the species of salamander or newt, and ensure the quality of the environment is carefully monitored and maintained.
There are three general types of tanks for salamanders and newts: terrestrial, semi aquatic, and aquatic. The information here is very general; species care sheets should be consulted for specific environmental needs (temperatures, etc.).
Terrestrial (Land) Tank
These are set up to approximate the environment favored by land dwelling salamanders. This sort of terrarium should provide areas of light and dark, damp substrate with leaves and or moss, and shelters made form rocks or small logs. Sufficient humidity must be maintained along with damp retreats. Generally, moss can retain enough water to provide the moisture/humidity needs of terrestrial salamanders. Water can also be provided in a shallow container as a water source and to help maintain the humidity. However, terrestrial species are not strong swimmers so the water must be shallow, and placing rocks or sticks in the water will help the salamander stay out of trouble (and will also prevent any prey insects such as crickets from drowning). A secure cover should be used; a screened cover helps with ventilation, but the top may need to be partly covered to maintain the necessary humidity.
Substrate can be a soil and moss combination, or simply peat and sphagnum moss. A layer of gravel can be used to line the bottom of the tank. Some species will use soil for burrowing, and mixing peat moss into the soil will help prevent packing of the soil and also increase its moisture retention ability. Keep in mind when creating the terrarium environment that the substrate will have to be changed as it becomes soiled, and the more elaborate the set up the more difficult cleaning becomes. For larger species or groups of salamanders will need to have their enclosures cleaned more frequently.
Shelters can be crated with rocks (make little caves), pieces of clay pots, or pieces of wood or bark. Terrestrial salamanders are fairly secretive and will spend a great deal of time under shelter. Therefore, placing shelters along the perimeter of the tank so you will be able to observe them through the glass. For very secretive species, black paper taped to the glass will provide the necessary privacy, and can be removed briefly to view the salamander.
This type of set up combines terrestrial and aquatic elements. A land area where the newt can bask with a transition to an aquatic area which can be quite deep is provided. The land area can be set up simply by piling gravel and moss above the water level, but it is easier in the long term to separate the land and water areas with a piece of plastic or plexiglass placed across the aquarium and sealed with aquarium grade silicone sealant.
It is important to make sure there is an easy transition from the water to land to allow the newt to crawl out. A dense piece of wood (e.g. ironwood, coralwood, monkeywood) can be placed part in the water and partly on land to provide the transition, and this also provides a nice basking spot. Alternately, gravel can be sloped in the aquatic side to provide a ramp out of the water. In the aquatic portion, the gravel should be large enough not to be swallowed, and should also be rounded and smooth to prevent skin damage.
A secure cover should be provided as some salamanders and newts can climb surprisingly well.
Aquariums are used for aquatic species (such as the axolotl), and provide a bit of a challenge due to the amount of waste salamanders produce, and their sensitivity to changes in their environment. Salamanders excrete a good deal of ammonia in their waste, and in the wild this waste is quickly diluted and carried away from the salamander's skin. In an aquarium, the salamander is essentially trapped with its waste, and the difficulty comes in keeping the water clean enough to keep the salamander healthy.
The first step is to keep the salamander in the largest tank possible to provide dilution. A good power filter should be used with larger aquatic species - most aquatic salamanders can tolerate fairly strong currents but but make sure the current is not too strong. Gravel can be used, but a tank with a bare bottom is easier to maintain and safer. Gravel that is too small may be ingested, and with large gravel, food can disappear between the stones.
In addition to filtration, frequent (partial) water changes are the best way to maintain water quality.
What Kind of Water?
Some experts recommend using commercially bottled spring (not distilled) water for housing amphibians. Tap water should always be treated with de-chlorinating tablets or solution, or left standing for at least 24 hours before adding to an aquarium to allow the added chlorine to dissipate. The use of rainwater is acceptable as long as it is checked for appropriate pH - it is often too acidic. Pond water is best avoided - it can be contaminated with pollutants or parasites that can be injurious to captive amphibians.
Under gravel filters work well in set ups that include gravel, since once established they support beneficial bacteria that convert ammonia to harmless nitrites. This type of filter can also be used in very shallow pools, even those set up in terrestrial terrariums. They also have the advantage of not creating strong currents, which can cause problems for smaller species. Because debris is pulled down into the gravel with this system the gravel will have to be cleaned (e.g. with a gravel washer) regularly.
There are a variety of other filter types available that are also effective. Inside corner filters with external air pumps are also a good choice for smaller salamanders since they do not create strong currents and also establish the beneficial ammonia converting bacteria. Whenever a filter is changed, add some used filter material to the new to speed the colonization of the good bacteria. Some of the stronger filters such as external filters are probably best reserved for the larger species that won't be stressed by strong water currents.
Ammonia is a waste product excreted by amphibians (and other animals, particularly aquatic species) that is dangerous if allowed to accumulate in their environment. The best way to prevent accumulation of ammonia is to use adequate filtration and replace water (not simply adding water, but draining and adding more). About 20-25% of the water should be replaced every week or every other week (you may want to get an ammonia test kit to see how fast ammonia levels accumulate). Even if changing from dirty tank to clean water, do it gradually, as the shock of changing water chemistry can be harmful even if it is an improvement in overall water quality (never do a full water change!).
pH and Water Quality
Generally speaking, salamanders do best at a pH (measure of the acidity) of 6.5 to 7.5, in the water and the soil. Ideally, if collecting salamanders from the wild, measure the pH of the soil and water in the area and match that pH in captivity. pH strips give a quick and easy measurement, and the environment should be checked periodically as the pH will change over time with waste production etc. If you are moving an amphibian to a new environment with a different pH it should be done gradually.
If a salamander is stressed due to an incorrect pH it will be restless, moving around in areas it usually does not, and eventually will become lethargic and have decreased muscle tone.
Most salamanders from temperate climates are best kept at fairly low temperatures of 50-70 F so heating is not a concern unless keeping sub tropical or tropical species. Often a basement is a good place to keep salamanders.
For some species, cooling may be necessary. Long term cooling can be difficult (some people rig up methods of running cool water through the tank), and it is probably best to simply try to set up tanks where the ambient temperature remains cool enough to keep the tanks cool. Air conditioning the room the tanks are in can be used if necessary. For short term cooling, you can do frequent 20-25% water changes with slightly cooler water, float small bottles of ice water in the tank, or even make ice cubes out of treated (dechlorinated) water to add to the tank as necessary in hot weather.
If supplemental heat is necessary, a submersible heater can be used in the aquatic tanks. Other heating methods such as incandescent lighting, under tank heaters, or other commercial heaters should be used with caution since they can be too drying for amphibians.
If tanks are kept in the basement, it is best to keep them near a window so that natural seasonal light cycles are maintained. This level of light is fine for most species. If live plants are used in the tank, though, a full spectrum light source is needed for the plants, and it is best to approximate the natural light cycles for that particular salamander. A low wattage fluorescent light is preferred if a light is needed since most salamanders and newts prefer darker conditions (and the lights should only be on a maximum of 10-12 hours per day) and lights can be drying.
Cleaning is important, but it is necessary to remember the sensitivity of salamanders (and other amphibians) to chemicals in the environment. Unless there is a health problem, simple hot water can be used to clean aquariums and items in the aquariums. Letting tanks and furnishings dry in the sun is also helpful. New items should be carefully inspected for pests or decaying material, cleaned, and dried before adding to the cage. Rocks and other non porous items can be soaked in bleach solution and very thoroughly rinsed. Commercial disinfectants should usually be avoided, as it can be difficult to rinse all the residue and it takes very little exposure to some chemicals to serious harm or kill a salamander. They should particularly be avoided for porous materials like wood, as any residues can leach out over time and kill the salamander.