Heaters and Filters
Having set up your tank on a strong base and in a good location, you are ready to fit it out. The basic equipment for an aquarium includes a cover or hood for the tank, a heater, a filter, a light source, a thermometer, and various decorative items, such as gravel, plants, and rocks.
A heater is an essential element of an aquarium because you will probably be keeping tropical fish that require constant water temperatures of 24 to 27 degrees C (76 to 80 degrees F). Aquarium heaters are rated in watts of power. Figure on 1.3 watts of power for each liter of water in an aquarium (5 watts per gallon). So, for example, a 76-liter tank requires a 100-watt heater.
Aquarium heaters are adjustable and controlled by a thermostat. The thermostat and heating element are enclosed in a long glass tube that either hangs into the water from the side of the tank or is fully submerged in the water.
A filter is another important piece of equipment for your aquarium. The best filters perform both mechanical filtration to remove particles and chemical filtration to remove harmful chemicals resulting from the body wastes excreted by the fish. Filters also accelerate the exchange of oxygen for carbon dioxide (released when fish breathe) at the water's surface.
Many experts believe that the best of the new filters are those that hang on the outside-back of the tank. These filters take water in from a tube that hangs in the tank, pass it through a fiber mesh to filter out particles, then pass all or some of the water over a revolving wheel. The water then returns to the aquarium across a broad lip that creates a sort of small waterfall just above the surface of the water in the tank.
The entire filter, and in particular the wheel, becomes inhabited by beneficial bacteria that occur naturally under water. These microbes break down the deadly ammonia and nitrites that form in an aquarium and convert them into relatively harmless compounds called nitrates. And the water's trip in a relatively thin sheet over the spinning wheel and through the waterfall maximizes the exchange of carbon dioxide for oxygen.
