Tropical fish can be acclimated to a wide range of water temperatures, but they cannot tolerate constant fluctuations from day to night. A heater is used to regulate temperature from these daily fluctuations.
The standard setting for a heater in a freshwater fish tank is 76 degrees Fahrenheit (24 degrees Celsius).
How much power/wattage do you need? 3 – 5 watts of heat per gallon. Example: 5 watts x 30 gallon tank = 150 watt heater.
The most important feature to look for is a safety switch which automatically interrupts power should the heater develop a short. A shorted heating element will cause a temperature increase beyond 100F, killing all inhabitants. Yes, this is a rare occurrence but every hardcore hobbyist has crossed paths with an unlucky person who has experienced this.
Glass vs. Titanium: Titanium is much more expensive but won’t break. It’s suggested with large creatures that like to rummage through decorations, displacing everything. A glass heater which is the cheaper option is suitable for a peaceful community aquarium. We like high quality glass heaters especially for a community setting.
When installing a new heater, always leave it in the water for a few hours to acclimatize the glass to the current temperature and avoid cracking.
Styles that hang on the back of the aquarium are usually less expensive and are not sealed at the top and cannot be submerged. Most have a plastic hooks that clips onto the top trim preventing it from falling into the water. Suction cups are also used to keep it stuck to the glass. I prefer this style of heater as it looks tidy hanging along with my filter components.
Other styles are submersible which can lay at the bottom of the fish tank. They are also suctioned to the glass with suction cups. If you have frogs or creatures that will jump or try and escape, a submersible is a superior option as there is no gap available to escape from as opposed to the hanging heater.