Instructions
Fish Tanks
Install a heater in your fish tank. The three primary types of heaters are immersible, submersible and filter heaters. These heaters either hang on the tank, are submerged inside the tank, or heat water as it flows into the tank, respectively. The primary difference among these heaters is how they look on or in the tank, but all will help keep your aquarium's temperature warm enough for fish to thrive and consistent enough so that the fish do not experience shock.
Move the tank to a warm location. Set up the tank in an interior room that is not typically cold or drafty. Avoid windowsills and locations near doors where sudden gusts of frigid air might cool the water in your tank. Do not place your tank in direct sunlight, as this can also make temperatures inconsistent and can cause overheating.
Install a thermometer and check the temperature daily. Consult a fish handbook or your pet store to determine the best water temperature for the type of freshwater fish you own. Check the thermometer to see if the tank's temperature is near the recommended temperature. Also check for temperature fluctuations. If the water is significantly cooler than the recommended temperature or if it often drops suddenly, see if your heater needs repair or if you need to move your tank to a more consistently warm location.
Fish Ponds
Do not let your fish pond ice over completely. An iced-over fish pond not only ensures cold water for your fish, it also reduces air flow and traps in toxins. This can be deadly for your fish. You can't solve the problem of an iced-over pond by just breaking the ice. Instead, you need to prevent ice over.
Use your water filter to circulate water. Drop your pond water pump to the very bottom of the pond. This will circulate the warmer water at the bottom of the pond, keeping the temperature steady. This will prevent pond ice-over and keep fish warm unless temperatures reach about 20 degrees below zero, says Shane Cultra of Country Arbors Nursery.
Heat your pond with an outdoor pond heater. Floating pond heaters create a hole in the ice by being so hot that the ice around them melts. They also keep the pond water warm enough so fish do not freeze to death. According to Cultra, heaters like this work in any temperature, but they are electric, so they must be plugged in. Floating pond heaters are available from hardware, pet and farm stores.
How to Keep Freshwater Fish Warmer in Winter
While freshwater fish don't require water as warm as some tropical species, they can't survive in freezing water. They also don't react well to sudden drops in temperature or unsteady water temperatures. If you have an outdoor fish pond, a heater is a necessity during the winter. Even if you have a tank with a type of freshwater fish that don't usually require an external heater, such as goldfish, taking steps to keep your fish warm in the winter helps to prolong their lives.