Seamus Healy wrote this care sheet for viper boas:
Viper boas are one of the terrestrial snakes in the genus, spending almost all their time burried under dirty, wet leaf detritus mud and other ground litter waiting for something to wander by that's edible. In order to minimize stressors and provide an environment in captivity that allows the animal to fufill these natural behaviors, I always reccomend a loose substrate suitable for digging around in. I've had a lot of luck mixing that extremely fine cocoanut fiber (bed-a-beast or t-rex has one too) with larger bark chunks (again commercially avaliable through the pet stores or orchid litter works well if you can find nice, clean, pesticide free stuff) this gives you something that will retain moisture well and won't clump up or pack down too much as the animal moves around over and through it. To this I generally add large clumps of sphagnum and occassionally cork bark- just to provide additional "hides" a little closer to the surface. Candoia are not particularly active snakes and a lot of the activity of the vipers will be under the substrate but I'd still go with an appropriately proportioned aquarium (low and wide for the ground dwellers, taller for the arboreal species in the genus)... wouldn't bother with anything to climb on at all for the vipers, they're far too heavy bodied and fossorially inclined to make use of it in any meaningful manner... a twenty long aquarium is more than enough for any adult aspera, tens or even smaller for little guys... or any appropriately sized plastic tubs or bins.
Temps... undertank heating pads or heat tape are the easiest way to maintain them... although you're shooting for ambient temps around eighty, maybe a few degrees cooler away from the heat pad and I wouldn't go much higher than 83-85 on your warm end. make sure you're checking the temperature of the substrate itself rather than the wall of the enclosure ten inches above where the animal will be... and take special care to make sure the glass isn't heating up too much above the heat pad- they will dig and can come into contact with it. For the vipers at least... they don't tend to equate heat with light since they do most their thermoregulation underneath a couple inches of rotting leaves... my experience has been that they are pretty good at not cooking themselves.
Humidity and moisture... water bowl big enough to soak in and they will use it for exactly that, although excessive soaking should be looked at for an underlying cause. The substrate can be made damp but not wet... it should clump well when squeezed, you may even get a few drops of water out of it but it should not be watery mud. Moister patches in the enclosure are acceptible for the vipers, they're built to be rained on and I am in the habit of maintaining the humidity and the substrate moisture by simply pouring water into it and turning it over a few times or dropping some nicely soaked sphagnum into the enclosure to replace any that has dried out. Aim for an ambient humidity someplace between about seventy and ninety but keep in mind for the terrestrial species (like the viper) that they'll be down where the water is in the substrate most the time anyway, don't flood them out trying to get a plastic hygrometer to read a certain way.
Handling... avoid it as much as possible, most of them don't react too well to being poked. The teeth are small and they're nonvenomous so it's not a huge concern but it's stressful for the animal and when they nail you, sometimes they can loose teeth. Not a signifigant health concern but any open holes are an invitation to infection. I've actually got a couple fat adults who I take the time to hook for that exact reason- I'm not a guy who minds a couple needle-holes in my hands, most the time vipers can't even draw blood if they tag me, but these girls hit hard enough to pull their own teeth out with regularity so for their sake... they get hooked if I've got the time. Candoia can react to handling and stress in wildly varying ways; they aren't real prone to deficating on you unless you're in the middle of probing them (usdually not needed, the external differences make visual sexing a fairly safe prospect) but some will bite where some will just fail to respond at all or do a fair imitation of a ball python- don't take docility when handled as a sign that the animal is unstressed.
Feeding... fun one. They instinctively want frogs and lizards but can *usually* be weaned off those onto rodents if the animal is unstressed and the keeper understands the idea of a feeding trigger and what real tease feeding entails. Scenting, chain feeding, altering the environment in which the food is offered and trying live prey are all acceptible routes, it's rare for even a massive adult female viper boa to ever need anything bigger than a young rat pup (eyes closed but haired, or eyes barely open and crawling at MOST) so offering toothless, defensseless rodent prey live is easier to do than it is with bigger species. There are a lot of tricks and tips and methods that various people have tried with success (or without it) for getting viper boas onto rodents and the biggest of these is an appropriate environment and lack of being poked by their owner... but some of them just won't take rodents. Ever. Be ready to find a steady supply of frogs or lizards that have been treated to kill gut fauna if you have a new animal. If you get one that readily takes rodents... well... good choice. When feeding rodents, you're offering a prey item that has a lot more calories and fat than the natural prey species for the snake would have given equal prey mass... so for adults, watch the weight. Vipers are a heavy bodied, fat snake and you want them to be thick, if you hit a point where your little sausagesnake is seeing scale seperation when it bends or "rolls" that leave scales bent outward even when the snake is straightened... cut back the food. My adults eat somewhere between every ten and fourteen days as is appropriate to the individuals body weight when they're on rodents. Do not wait for them to deficate before feeding... they tend to hang onto things they have eaten for a good long while and will also often deficate in the substrate where it can't be easily seen (if you get lucky, you may have a waterbowl user). Which just means you should be switching that substrate out on a fairly regular basis. I'd suggest a seperate container and not a lot of light for a feeding bin if you're using the substrate I suggested above.
Other information you may find useful... They don't shed too often, with the viper boas being the slowest shedders with the thickest scales in the genus. I've got adults who shed about once every eighteen months and younger adults who may shed twice a year. The keeled scales are built to get dirty... they trap and collect substrate and get stained by soil so that the animal is a close mimic for the area it's in. Immediately after a shed (which also often happens under the substrate, you may or may not find the shed itself) the animal is usually a lot lighter and brighter for a few weeks, with it's patterning much more obvious. The little guys don't shed nearly as quickly or often as many other species either, but when growing they will shed more frequently than the adults.