Hermit Crabs require temperatures between 68 degrees and 74 degrees at all times. To keep the optimum temperature, try the Hermit Crab Heater from ZooMed, specially designed for Hermit Crabs. Made with plastic crab habitats in mind, this 4 watt heater is perfect for a terrarium of 5 gallons or less. Keep Hermit Crabs comfortable with a heater built just for them. Size: Heater is 7" x 4", has a 6.5' power cord.