Fish experts recommend using a fish tank thermometer and setting the water temperature at 18°-22°C (65°-72°F).

Stick-On (LCD) Thermometers Stick on thermometers are the most widely used thermometer in freshwater aquariums as they are often provided as part of the new aquarium package.

Stick on thermometers: placed on the outside of the aquarium, reading the temperature of the water through the glass. Can be affected by outside air temperatures, giving false readings. Glass thermometers: Placed inside the aquarium, attached to the glass with a suction cup.

Digital thermometers may need their batteries replaced and some have a probe on a cable that may have come out of the water, measuring the cooler room temperature instead. Use a second thermometer of a different type for a second opinion and peace of mind.