Crested geckos thrive at temperatures between 72 and 82 degrees Farenheit, general room temperature for many homes. While they deal fairly well if the temperature dips a few degrees below 72, you will want to avoid temperatures much higher than 82. The excessive heat can cause stress in the animal, which could put it off of its food, and possibly eventually kill it. If you have no means of cooling your home to below 82 in the hot months, a crested gecko is not a good choice for you. Using a digital thermometer and hygrometer to monitor temperatures and humidity is a good idea.
It is also a good idea to have a backup plan in place in the off-chance that your power goes out on a very hot day and you can not run your air conditioner. You can put the gecko in a watertight enclosure in a bathtub with a few inches of cold water inside the tub, or you could take a couple of bottles of ice and put them inside the enclosure. Having cooling packs on-hand can also be helpful. However, these are all temporary fixes and may not be sufficient to keep a crested gecko at the proper temperatures for long.
A single adult gecko should be given, on the low end, about 20 gallons of space; as they are arboreal, it is preferable that the enclosure be taller than it is longer, though larger long tanks can be used too as long as there are a lot of good climbing spots provided. Set up good thick branches which can support the gecko's weight. If you acquire branches from outside, they should be carefully baked in an oven, and frozen for 24 hours if possible, to attempt to kill off any infesting bugs. Bamboo can be a good sturdy climbing material, and can often be found in craft stores, home improvement stores, and even some department stores (but please stick with the kind that isn't dyed/painted).
With any kind of setup, it is important to keep in mind that no matter what kind of substrate you choose to use, your gecko may have a risk of ingesting it, and impaction can occur. While this is less likely to occur if you use something like paper towels, even small bits of paper towel may sometimes be consumed accidentally. Crested geckos are clumsy hunters at times! They may see what they think is a prey item, make a lunge, and get a mouth full of substrate. If you use soil-based substrates, you can help your gecko avoid choking or impaction by making sure the soils are broken down finely, with no loose pebbles or sticks in the mix, and most importantly, by keeping your gecko well-hydrated so that ingested soil can easily pass through the animal's system.
For a simple setup, the floor can be covered in whole paper towels, and fake wide-leafed plants can be used for cover. Adding coconut hides, decorative pots with a hole carved out, or other items for the geckos to nap inside can help them feel more secure during daylight hours. Droppings should be removed daily, and the paper towel substrate should be changed at least weekly. They may also walk through their food and track it around, which can get a bit nasty-looking on paper towel and the glass of their enclosures.
For a naturalistic setup, some people recommend using coco bedding, some use eco-earth, some use leaf litter, some use moss, some use a mix of some of these things. I recommend doing a lot of research before settling on a naturalistic substrate, as crested geckos - especially nesting females - will dig into the soil often using their heads/faces as "shovels," which means some substrate may be licked off or swallowed. Never use non-organic soils, or soils with pesticides or fertilizers added, as these chemicals will harm your geckos. Avoid large-particle bedding like bark chips, as the pieces may be ingested and are very difficult for an animal as small as a crestie to pass.
When I make naturalistic setups, I like to have a base of 1 to 2 inches of hydroponic balls, cover those over with a nylon screen, and then add in my soil mixture, which is generally a mix of organic soil, sphagnum peat, leaf litter, and ABG mix, all of which have been broken down well with any hard clumps removed. For crested geckos, you can also add "cleaning crew" bugs like isopods and springtails to the soil, and I like to mix in a little bit of earthworm castings for natural fertilizer as well for the plants.
A good hardy plant for naturalistic setups is the pothos - they're very easy to keep, eventually grow in a viney manner, and they have flat wide leaves which are perfect for the geckos to walk on. Some bromeliads have beautiful wide leaves that add color to an enclosure and offer a nice place for the gecko to sleep, as well. When choosing non-toxic plants for your bioactive enclosure, try to lean toward plants that can stand up to the abuse of a jumpy, clumsy gecko!
On the controversial topic of cohabitation, or housing geckos together: I heavily recommend that new keepers do not attempt this practice. It can take an experienced eye to see when something is wrong, since these animals tend to hide injury or illness. If you do choose to house crested geckos together, always keep an eye on your geckos and watch for tail nipping, crest biting and other injury, weight loss, or other issues that may indicate that your geckos are fighting with each other, and be prepared to separate them. Males and females should never be kept together unless the female is of appropriate size (I recommend 2 years of age and steadily retaining a weight of over 35 grams, with more being encouraged) and with the understanding that you have done a slew of research on the effects of breeding on your animals. A male will breed a female if they are housed together, once he has hit maturity.
You should consider not housing males together, as they can have a tendency to fight with each other. After proper quarantine, some keepers do choose to house animals together. If you go down this route, please continue to keep an eye on animals. Every new animal introduced into an enclosure increases the chances of problems popping up as these animals tend to see other geckos as either competition for food, competition for resting spaces, or something to mate with. Geckos of different sizes should also not be housed together, as a larger gecko can intimidate a smaller gecko away from food and resting spots, or cause injury to smaller geckos.
Even if you consider yourself experienced, a good rule of thumb is to never get more geckos than you have single enclosures or space for. The day may come when you need to separate animals immediately!
Smaller juveniles and hatchlings can be housed in smaller enclosures, so that they may more readily find their food sources. Hatchlings can fare well in a Kritter-Keeper/Faunarium enclosure, generally for a few months, as long as there are leaves and a small branch or two to climb on. A caveat on Faunarium setups: They do have a lot of airflow. This can be good in the humid summers, but in winter when many people have heat running often, these types of enclosures can dry out a bit too quickly, so you may wish to cover some of the holes in the enclosure with plastic wrap or cover part of the enclosure with a small, slightly damp towel. As with adults, keep in mind that even juveniles can squabble, and may especially bite a cagemate's tail, so be prepared not to house even hatchlings together. If you choose to house your smaller/juvenile geckos in larger enclosures, I recommend offering several small feeding stations so the gecko can easily find food and thrive.
It is important to give your gecko a rotating day-and-night cycle; they should have at least 8 hours of darkness as well as light. I essentially allow my geckos about the same amount of daylight as we are currently seeing; if the sun is coming up for me at 7 AM, I have their lights turn on at 7 AM. If the sun is setting at 6 PM, their lights go off around 6 PM. This helps regulate breeding females especially, as a shorter day period helps tell their bodies, "It's winter, and time to rest!" and they cease producing eggs.
Because crested geckos are nocturnal, there is still some debate as to whether UVB-type lighting is required; during the day when the UVB would be turned on, many crested geckos do all they can to hide under leaves and inside hides, where the light would not affect them. Because of this, many breeders do not use UVB lighting. If you choose not to make use of UVB lighting, it is important to at least make sure your geckos get a cycle of ambient light (light through a window should never hit the cage directly as it could cause a drastic increase in temperature) or indoor lighting. Keep yourself informed about the uses of UVB lighting with crested geckos by searching out forums and publications about their keeping.
Crested geckos in the wild enjoy soft, ripe/overripe fruit items as well as live insects. In the past, many crested gecko breeders swore by using fruit baby foods supplemented with necessary vitamins and minerals. However, more recently, many different pre-packaged crested gecko foods have come out onto the market. My geckos are currently thriving on a mix of diets which include Pangea Fruit Mix (original), Pangea Fruit Mix (Complete), live Blaptica dubia roaches, and a variety of blended fruits. Pangea Fruit Mixes can currently be found at Pangeareptile's online store.Please note that not all geckos enjoy all foods equally. It can be a bit tricky to figure out what works for your geckos but please keep in mind that not all pre-packaged foods are created equally. As with dog and cat foods, there are some on the market that are just not decent for your animals. Avoid foods whose ingredients lists start with low quality ingredients like corn, tomato pomace, and other fillers.
My warm-weather feeding schedule is approximately as follows:
Monday: Feed (approx. 1/2 tablespoon mixed per adult), and mist geckos.
Tuesday: Leave food in enclosure and mist geckos.
Wednesday: Replace old mix with fresh, mist geckos.
Thursday: Leave food in enclosure and mist geckos.
Friday: Replace old mix with fresh, mist geckos.
Saturday: Leave food in enclosure and mist geckos.
Sunday: Remove food, offer 3-6 roaches in enclosure for each gecko and mist geckos.
Monday: Remove roach dishes and mist geckos. Etc.
I currently use Blaptica dubia roaches, though other acceptable feeders are crickets and Calci-worms/Phoenix worms/soldier fly larvae. I do avoid harder-shelled feeders like meal worms, as these lower-temperature geckos' digestive systems do not always break down the shells well and I have found large portions of undigested mealworms in the feces. I also try to avoid very fatty feeders like waxworms. Live food is always dusted with proper supplements and gutloaded (fed good foods before feeding to the geckos), as appropriate.
Also, once or twice a month, my geckos will receive a treat of crested-safe fruits like papaya, fig, mango, blackberries, raspberries, and blueberries. Essentially, they get fresh treats from the breakfast I had that day. I do avoid citrus fruits like oranges, lemons, and pineapples, and I try to use smaller amounts of fruit with a low calcium:phosphorous ratio like bananas and peaches.
(I note here that during the cooler winter months, my crested geckos tend to eat less due to lowered temperatures, and I will feed every third night instead of every second to avoid food waste. However, all geckos are still misted every night as needed.)
If you are still thinking of feeding your crested gecko a baby food diet, please visit Dragontown Reptiles and meet Bubba. This animal had to be rehabilitated and will never be 100% "normal" due to his past diet.
Some of my adult male geckos just plain don't care for feeder insects - they won't look twice at a cricket or roach even if it's crawling on their snout. But I do heavily, heavily encourage the inclusion of feeder insects even with a "complete diet," and the ones who enjoy them receive about five appropriately-sized crickets, or three or four roaches, once every week, and sometimes twice for breeding females. Feeder insects should be gutloaded with proper foods and they can be dusted with a calcium supplement (which are also available at the Pangea store linked above). A general rule of thumb is that feeder insects should not be wider than the space between a gecko's eyes, though my crested geckos often enjoy slightly larger roaches. I am currently feeding Blaptica dubia roaches and have had great success with this species, as they can be put in a small cup inside the geckos' enclosures and do not go free-roaming. Generally starting at around 2 weeks of age, my geckos are offered these roaches and it will usually take them several times offering these foods before they get the idea that it's something they can eat. It is helpful to make sure to put the roaches in a container the gecko can easily look down into from a favorite perch, and not to use something that is so huge the gecko cannot get back out again.
Catching your own feeder insects from outside is not recommended; outside bugs may have parasites, or they could have walked through or eaten insecticides or other chemicals which could potentially poison your gecko. Purchase your feeders from a trusted source, or raise your own from a trusted source's stock.
Adult crested geckos should be misted thoroughly in the evening up to about 90% humidity (you can use a hygrometer to gauge the level); during the day I allow humidity levels to lower again to about 50-60%. Proper humidity will help with shedding, and the geckos will often drink water from available leaves. I also like to leave a shallow dish of water in the enclosure for adult geckos, and a very shallow dish (milk jug cap sized) of water for very small geckos. They are not often seen lapping water out of these bowls, but they do occasionally use them, and they can help regulate the humidity in the enclosure.
Important tip for new keepers: Please keep in mind that keeping the geckos in a sodden environment at all times may lead to skin infections and trouble shedding, so allowing a dry-out period through the day is essential for healthy geckos. One of the biggest mistakes new owners make is attempting to keep the environment too moist. Imagine their shedding skin like taking off socks at the end of the day. They slide right off if they're dry, but they can stretch and stick and be generally more difficult to peel off if they're soggy!