Basic Filtration Principles

• Polluted tank water is pumped through the various compartments within the body of the filter. Large pieces of waste matter, such as decaying aquatic vegetation and uneaten food are trapped by the mechanical filter and removed from circulation. Water, now devoid of this waste, passes over chemical filter material that further polishes it and removes coloration, gasses and other undesirable products. Biological filter material then purifies the water of toxic products.
  
  

Mechanical Filtration

• The mechanical filter material will trap gross particles of detritus and leftover food. This material prevents decaying organic matter from coating and smothering the chemical and biological filter medium. The mechanical filter material should regularly be rinsed out or changed. Although dirt gets trapped within the material, it continues to decay within the water and is best removed through regular cleaning or replacement of the filter material.
  
  

Chemical Filtration

• This filter material incorporates activated charcoal to remove molecules of fish urine and other toxic metabolic waste. Molecules of these waste products are trapped within the microscopic holes and passageways within each piece of activated charcoal. Since this material eventually becomes exhausted, the chemical filter material should be replaced monthly.
  
  

Biological Filtration

• Beneficial bacteria break down the toxic waste products of fish, by converting them from into less harmful products. Aerobic bacteria that require oxygen, convert ammonia to nitrite (NO2-) and further to nitrate (NO3-). These bacteria coat the outer surfaces of the biological filter material, where there is abundant oxygen and water movement. Anaerobic bacteria, which can only survive in oxygen-deficient environments, reduce the nitrate and effectively remove it from the water. These bacteria colonize the interior of the biological filter material, where oxygen levels are almost non-existent.