Heating Your Aquarium

Because aquarium fishes are usually referred to as “tropical” fishes, the idea has become erroneously established that they require high temperatures for survival. The truth is that 75° F. is warm enough for tropical fishes, with rare exceptions. In fact many of our aquarium inhabitants are only semi-tropical; and will thrive in even lower temperatures.

Your main concern should be with temperature extremes and temperature fluctuations. Too extreme a fluctuation, even within the favorable range, can lead to difficulty. Fluctuation even within the fishes’ range is the problem that is usually the most difficult to solve. For example most tropical fish are comfortable within a low of 70° F. and a high of 85″ F.; 75° F. is considered ideal. But suppose that the tank’s position is near a radiator, or in a sunlit area, or that the wattage of the reflector bulbs is too high. Any one of these could cause the temperature to rise to 85″ F. during the daytime. These sources of heat are not present during the night and the tank’s temperature may drop to 70° F. This gives a fluctuation of 15° F. in twenty-four I hours. Fishes continually forced to adjust themselves to such temperature changes are under a definite strain; they become weakened and subject to disease.

Considering the abuses to which they are frequently subjected by well-meaning fanciers, they are remarkably hardy. I have seen fishes subjected to such extreme cold hat they floated torpid and, to all appearances, lifeless at the surface. When warmed up - and in these cases If was a fairly rapid warming - they recovered promptly and vigorously. Moreover, fishes seem to be capable of swimming without difficulty through strata of water at different temperatures. A reflector might raise the water’s surface temperature 5° or 6° higher than the bottom temperature, yet the fishes swim up and down with no sign of discomfort.

There is a school of thought which holds that it is necessary for the temperature to fluctuate a few degrees between day and night in order to more closely duplicate f he fishes’ natural environment. This hardly seems necessary. Inhabitants of aquariums with controlled temperature fluctuation appear to be in no better condition than I hose in aquariums maintained at a constant temperature.