Aquarium Water Temperature

For the vast majority of tropical fish, an aquarium water temperature of 76 to 78º Fahrenheit will be fine. Some species like cooler water and some prefer warmer water, but as a compromise, this range works well.

If you are having difficulty deciding what fish to buy, it wouldn't hurt to choose fish that prefer the same temperature range. Goldfish are not tropical fish and fare better at temperatures closer to 65º Fahrenheit.

It is very important that the water temperature be consistent. Rapid fluctuations in temperature, particularly down, may cause physical stress to fish that often leads to disease. The solution to maintaining the correct water temperature is an aquarium heater and thermostat.

Aquarium heaters are available in a variety of types, sizes, and prices. When it comes to aquarium heaters, trying to save money is not a good idea. The reliability of a heater is too crucial to risk buying an inexpensive one.

The weak link in any heater is the thermostat, which regulates the heater, turning it on and off to maintain the desired temperature. The quality of design, materials, and construction of the thermostat is one of the things that separate unreliable heaters from good ones. In cheap heaters, the thermostat often sticks -- either open or closed -- and this can be disastrous.

Aquarium Heaters

As a general rule, the more water a tank holds the more stable the aquatic environment will be. For example, it will take a 50-gallon tank much longer to drop in temperature than a 10-gallon tank.

The same is not true for temperature increases, though, because the aquarium heater wattage is chosen to match the size of the tank it will be in. The rule of thumb is five watts per gallon, which will allow the heater to raise the temperature of one gallon of water by one degree Fahrenheit in one hour.

Thus, a 10-gallon tank would use a 50-watt heater and a 50-gallon tank would use a 250-watt heater. For larger tanks it is often necessary to use more than one heater to achieve the desired wattage.

In fact, using more than one heater is actually a good idea for any size aquarium in terms of safety. When two smaller heaters are used that equal the wattage of one heater, the possibility of complete heater failure is almost eliminated.

If one heater should stick in the closed position, the temperature will raise only half as fast, giving you a greater chance of catching the problem before it becomes serious. If one of the heaters sticks in the open position, the other heater will prevent the temperature from dropping as far or as rapidly.