Aquarium Thermostats
Since the majority of tropical fish come from waters where the temperature is rather constantly above 75° F., you must see that the temperature of the water in your aquarium never drops below that point. A thermostat, composed of a bimetallic strip that bends backward and forward with each rise and fall of the temperature, will make this easy. This bending action can be utilized to make and break an electrical circuit.
An electrical heater in the circuit will go on when the circuit is completed. As soon as the water in which the thermostat is located reaches a predetermined temperature, the bimetallic strip bends away from its contact and breaks the circuit, thus shutting off the heater. Almost all thermostats can be regulated by a set screw that moves closer or farther away from the bimetallic strip as it is turned.
By regulating the distance from the screw to the strip, the temperature at which you want the thermostat to operate can be regulated. Most thermostats fail to operate because of corrosion on the point of contact between the thermostat and the set screw. It is advisable to check on this factor every few months. Sometimes it is good to run a nail file over the contacts to make sure that conducting surfaces are in contact. Of course, the thermostat has to be readjusted after such a treatment.
Many thermostats are located in the same unit as the heater. Thermostatic units which are located separately from the heater, besides being most advantageous, are usually most economical, since more than one heater can be operated from a single thermostatic unit. When operating such a system, it is advisable to use a thermostat in the smallest tank as far from the heater as possible, as smaller bodies of water are liable to more drastic temperature changes. When operating a great number of heaters from a single thermostatic unit, the wattage
rating of the thermostat should be checked. Thermostats are all rated at the maximum safe load they can carry, and if overloaded they will burn out. When overloaded, the spark that jumps across from the bimetallic strip to the set screw will be so hot that it will actually weld the two units together. This can be most disastrous since the thermostat will not be able to turn off the heater and the fish will be cooked to death. To calculate whether the load on the thermostat is safe, add up the total wattage of the heaters and be sure that it does not add up greater than the wattage rating of the thermostat.
Many thermostats are built with condensers (capacitors) to eliminate static or interference in radio and television sets. These capacitors are easily added to any unit that does not already have one. They may be easily installed by placing them across the circuit at any point. If you are skeptical about your ability to make this minor adjustment, let your electronics man do it.
The quality of a thermostat can generally be determined by the material of which the points of contact are composed. Silver contacts are usually the only low- priced acceptable contacts.
