A ten or twenty gallon tank is good for two to four small hermits.  A twenty to forty gallon tank is good for a dozen small or three to four large hermits. Hermit crabs are social animals and should have at least two other crabs with them.  The proper home for your crabs should be one that holds in humidity, but still lets in fresh air. A fish tank or reptile aquarium usually does nicely. You can even rinse out that old leaking tank from the attic and use it! Acrylic terrariums tend to work better, as they hold the humidity and heat more efficiently. You should buy a hygrometer (humidity gauge). These will help you to monitor and maintain a 75-85% relative humidity. Hermit crabs breathe through (hardened) gills, and can't breathe properly unless the air is humid enough. The ideal range is at least 75% relative humidity. Humidity lower than 70% will cause suffocation, which kills slowly over several weeks or months and is extremely painful. A great way to increase your tank's humidity naturally is to add natural moss to your tank. It increases the humidity, and hermit crabs eat it. Look for moss like Fluker's Reptile Moss at your local pet store. Sponges also work well, and can also be found at a pet store. But sponges get dirty easily and need to be changed out every two to three weeks. Hermit crabs are tropical animals and do best in warm temperatures. 75-85°F is the proper temperature range. Heat damage is irreversible, and temperatures that are too low slow down a crab's metabolism. An under-tank heater designed for hermit crabs, mounted on the back of the tank is a good way to keep your tank humid. An improper environment can cause your crab to become lethargic and inactive, lose limbs and could potentially cause death. Buy a thermometer to keep an eye on the tank's temperature. Substrate is the layer of material you place on the floor of the tank. Sugar-sized arrogate sand is the only sand you should use because other grades could cut the crab, and play sand may have harmful fills. Use dechlorinated salt...

TL;DR in Vietnamese:
Hãy chọn bể kính có kích thước phù hợp để làm “crabitat”. Đảm bảo độ ẩm cần thiết cho bể nuôi. Đảm bảo nhiệt độ thích hợp cho bể nuôi. Chuẩn bị chất nền. Giữ cho lớp nền sạch sẽ. Mua đồ chơi cho lũ cua. Chuẩn bị cho bầy cua của bạn chỗ trú ẩn. Thêm một số loại thực vật sống vào bể của bạn. Cung cấp nước cho ốc mượn hồn. Đảm bảo nước đã được khử clo.