The all new Cobalt Aquatics MINI-Therm compact and fully submersible heaters feature a constant ON design, specifically for small aquariums up to 5-gallon. The heater casing is made from a thermal-plastic polymer that is shatterproof. An internal ceramic heat radiator that provides even and the best heat distribution from the heating elements. Perfect for freshwater and saltwater aquariums and terrariums. Available in 3 sizes that will raise recommended size aquarium temps up to 10 degree. 10-watt- 2.4-gallon.