Tips on Choosing an Aquarium Heater

A submergible heater is usually placed flat along the bottom of the tank. The theory is that as the warm water rises it will cause a mild circulation within the tank, insuring a more even distribution of heat. Whether this particularly benefits the fish in most home aquaria is doubtful. However, with the heat source at the surface of a tall tank, and with no aeration or filtration, you will note a considerable disparity in temperature between the upper and lower strata of water. Whether the difference, except in an extreme case, is enough to discomfort the fishes is problematical. In nature, fishes swim with no apparent signs of discomfort between the sun-warmed surface and the cooler depths. They appear quite capable of adjusting to this type of change with no noticeable signs of stress.

By encasing the heater and thermostat in separate tubes, one is enabled to place the heater in one corner and the thermostat in another. This is supposed to insure a more even distribution of heat, since the heat must travel through the entire tank to reach the thermostat. In theory it is all right, but in actual practice it has hardly proven necessary. Water circulation itself distributes the heat readily enough.
For the advanced hobbyist who can afford it, the most practical method for heating all your fish tanks is a tank room. The temperature in the room can then be thermostatically controlled and heated by the use of a commercial space heater, either gas or electric. A small fan can be used to assure an even distribution of heat within the room.

If this method is impractical, you have your choice of either of two methods, or a combination of both. The simplest way is to get a combination heater and thermostat for each tank. There are a number of low-cost combination units on the market which will give very satisfactory service.

An alternative method is to get a high-capacity individual thermostat. This is placed in the smallest tank of the series to be controlled with the single setup. Heaters with wattages proportionate to the size of the tanks they are put into are connected in series with the thermostat. For the average home, allow 5 watts to the gallon. For a 5-gallon tank, use 25 watts; a 10-gallon tank, 50 watts, and so on.

For example: a hobbyist with four tanks, a 5-gallon, a 10-gallon, and two 20-gallon tanks would use the following: a 25-watt heater in the 5-gallon tank, a 50-wa heater in the 10-gallon, and a 100-watt in each of the 20’s The thermostat to which all the heaters are coupled placed in the smallest tank. Why? Because the smaller the amount of water in a tank, the more subject it is to fluctuation. Should the thermostat be placed in the largest tank, the smallest one might show a drop of as much as 5 to 6 degrees before the temperature of the large one would drop sufficiently to activate the thermostat.