Protect your fish from unsafe temperatures with the fully submersible Digital Aquarium Thermometer. Simply affix the thermometer to the inside of the aquarium (below the water line) using the suction cup attachment, and you're ready to go. This thermometer reads in celsius only, and can be used for freshwater and saltwater aquariums.
This is fully submersible, and completely safe within the water. It measures water temperature accurately within 1°C, and has a large, easy-to-read LCD display.