What Happens if I Have a High Watt Aquarium Heater?

You need to have enough heater power to keep your aquarium at the right temperature for your fish. However, you won't get penalized for having too much heater power, so long as you use your heaters right. If anything, extra wattage give you more control over your aquarium temperature and can give you some leeway in certain situations.

  1. Guidelines

    • Most guidelines for selecting an aquarium heater focus on watts of heater power per gallon of aquarium volume. For aquariums larger than 30 gallons, you need about 3 watts of heater power per gallon. For smaller aquariums, you actually need more heater power per gallon, ideally at least 5 watts per gallon. While it might seem counter-intuitive, smaller aquariums need more heater power because they lose heat more quickly, since they have greater surface-area-to-volume ratios than larger aquariums. If you have more wattage per gallon than these guidelines, it just means you can more easily control your aquarium temperature.

    Multiple Heaters

    • Ideally, you want to distribute your wattage across more than one heater. This gives you a safety net in several situations. If one heater gets stuck in the "on" position without you noticing, it will cause less impact than if you have one big heater and the same problem occurs. At the same time, aquarium heaters sometimes wear out. If one of your heaters fails, the other one can slow heat loss long enough for you to replace it.

    Using Heaters

    • If you have more wattage than the guidelines call for, the only difference is that you need to exercise more diligence when setting your heater since the extra wattage makes it easier to overheat your aquarium. To set the heater, turn the dial until the indicator light turns on. Take care to turn it just enough to get the light on, and no further. Watch the temperature carefully through this process. If the heater turns off at the desired temperature, don't adjust it further. Avoid raising the temperature more than 2 degrees Fahrenheit per day, since sudden changes in temperature stress fish.

    Accommodating Multiple Heaters

    • If you have one or two aquarium heaters, you should be able to hide them among aquarium plants or other decorations well enough. However, if you have a sump -- which is more common in saltwater aquariums -- you have the option of hiding them out of sight. If you keep your heaters in the main aquarium rather than a sump, you may need to consider heater guards. Heater guards consist of a plastic sheath that allows you keep aquarium critters away from the heater. Many marine organisms will rest on aquarium heaters, not realizing the entire thing can turn on suddenly and harm them. On the freshwater side of things, certain large cichlids may attack heaters, mistaking the blinking light for a rival fish. In this case, a heater guard, or carefully hiding the heater in rockwork, can protect it.