Fire salamanders are easy to maintain.
I have found that most salamanders/newts do best in sexed pairs. If you keep adult fire salamanders of the same sex together, especially with S. s. terrestris, chances are only one pair will put on much weight and breed, because one pair will come to dominate the enclosure.
You can maintain a pair of fire salamanders in a standard twenty gallon tank over a soil/moss substrate. I use a mix of the following:
60% topsoil, 40% peat moss. Avoid using ony ground peat moss, as it sticks to the animals and may be swallowed. Plain topsoil tends to become a mouldy, muddy mess if used alone. Place the substrate over an inch of pea gravel.
Another alternative: long-stranded sphagnum moss over rinsed pea gravel: I have found this works very well.
Substrate must remain moist at all times, although some recommend providing the animals with a dry area. Give each salamander its own hiding place. Provide a water bowl that they can easily got in and out of on a regular basis. The animals should be provided with clean water that is free of chemicals such as chlorine and heavy metals.
Hides: cork bark and those clay pipes you can buy at department/garden stores are great.
Temps should not go above 70F. To get around this problem in summer, I place those small cold packs in a bag and bury them in the substrate. Also, bulking the animals' enclosure up with sphagnum will help increase evaporation and will help keep them cool.
Plants that are good for fire salamander terrarium: pothos, small ferns such as braken ferns, and clover. Regular full-spectrum light will suffice for these plants.
Diet: most settled fire salamanders kept between 60 and 70F will chase down crickets, mealworms, and waxworms. Earthworms are a fav as well, and they also will eat snails supposedly (I've never tried it). Diet sups such as Rep-Cal can be added. adults should be feed 3 times per week, young animals every other day.
Breeding: I place my sals in one of those plastic Reptile Ranches you can buy at Wallymart. I fill the conatiner with moist sphagnum and place the animals in our outdoor laundry room, were temps stay at about 40F. I fast them for two weeks prior and keep them in hibernation for three months. When I bring them out, I place them in an aquarium with a spongue filter and a hood. One of the nice things about maintaining newts and sals over the sphagnum moss/gravel layer setup is you can remove the moss and fill the tank with water slowly over a few days. When you remove the adults, you maintain the tank as an aquarium, then slowly drop the water level as the larva transform. After a while, you have remove the water/it evaporates and you replace the moss. Vola! Your tank is terrestrial again. If you keep a pothos in the tank, you can leave it in the enclosure when you convert it into an aquarium.
Feeding you sal larva: buy daphnia from a local cllege or Carolina Biological Supply. Brine shrimp also make a nice meal occasionally, as will fruit flies/pineheads dropped on the water surface. Newborn guppy fry also make a nice meal for larger larva (I've never tried the later, so good luck). Do not leave fish in the tank, however, as they may grow and harrass the larva. Large fish and young amphibians do not mix.
Hope this helps.