Marina LCD Aquarium Thermometer. With water temperature being such a critical factor for the well-being of fish, it’s important to have a good thermometer. This Marina LCD horizontal/ vertical mount liquid crystal thermometer provides accurate and easy to read temperatures readings in Fahrenheit and Centigrade. Ideal for all fresh and saltwater aquariums, the thermometer comes with an adhesive backing that makes mounting to the outside glass easy. Available in the following Models: 8 cm (3.125 in) ; 20 to 30° C (68 to 86° F). 7.6 cm (3 in) ; 19 to 31° C (66 to 88° F).