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Keeping tropical fish through a New England winter

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A New England winter is hard on a tropical tank: rooms get cold at night, thermostats get turned back, and ice storms cut the power. Here's how to plan for it.

Size the heater for the room, not the summer

A common rule of thumb is 3–5 watts per US gallon, at the high end for colder rooms: about 5 W per gallon below 68 °F, 3 W per gallon in a 72–76 °F room. A tank by a window or in an unheated room needs more. A 55-gallon tank, for example, needs roughly 165–275 W, from one 200 W heater or two 150 W heaters. Two smaller heaters also give you a backup if one fails.

Allow for the thermostat

Turning the house thermostat back 7–10 °F for 8 hours a day can save up to 10% a year on heating, according to the US Department of Energy. That's a good habit, but it means the fish room is coldest overnight, so check the heater copes with the coldest hour, not the average.

In a power cut

• Oxygen usually runs out before warmth does. A battery air pump is the most useful thing to own.
• Keep the lid on and wrap the tank in blankets, towels or Mylar, leaving a small gap at the top for air.
• A small battery backup (UPS) can run an air pump and sponge filter for many hours, but only a short time if it also powers a heater or canister filter.
• Small tanks lose heat fastest.

We breed rare fish, plecos and shrimp in Groton, Massachusetts. See also our New England water guide.

Sources: Aquarium Co-Op on heater wattage and power outages; Aquifarm on battery backup; US Department of Energy.