Aquatics - Aquarium Filtration


Mechanical Filtration Part 1

  • knowing the basics can help avoid filtration problems and understand how to deal with them when problems occur
  • mechanical fitration traps particles of uneaten food, fish waste, decayed plant materials and other aquarium debris
    • mechanical filtration is the first stage of the filtration process
      • should always be placed so that this is where aquarium water hits first
    • most mechanical media promote the colonisation of beneficial bacteria
      • particularly sponges or pads
    • biological filtration is not the main function of this media
      • but cleaning and changing this media will impact the biological capacity of the filter
  • types of mechanical filtration media, which are dependent on the type of filter used
    • some filters have pads, some have sponges, other have filter wool
    • in some cases, mechanical filtration media is designed to hold chemical filtration media
      • e.g., cartridge media used in some power fibres
    • materials have a range of coarse to fine, thus allowing for different degrees of filtration dependent on the pore size
    • some filters have multiple layers of mechanical media, the coarsest being placed first to remove larger particles first
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Mechanical Filtration Part 2

  • Sponges, pads or foam blocks are used in canister filters and some power filters
    • sold in rectangles, square or circles to match the opening of the filter basket
    • some may have several pore sizes available which should be matched with the purpose for what they are used
    • a very fine pore size may clog too quickly if used first in a filter
    • there are filter sponges that fit to the powerhead or filter intake to reduce water flow as well as provide filtration
  • filter wool or floss is used in a variety of filters 
    • originated from tank box filters
    • continues to be used in canister and wet/dry sump or trickle filters
    • can be used when the carbon filter is removed, and stuffed in its place
  • combo cartridges are often used in power filters 
    • combines the mechanical and chemical filtration
    • the exterior of the cartridge performs mechanical fitration
    • the media provides chemical filtration
    • carbon media should be discarded and replaced regularly 
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Biological Fitration

  • biological filtration uses bacteria to remove potentially harmful substances from an aquarium
    • when bacteria in the tank 'eat' any compound, including ammonia, nitrite and nitrate
  • converts one chemical substance into another
    • ammonia to nitrite to nitrate
  • multiple types of bacteria are used in biological filtration
    • nitrifying bacteria: remove ammonia and nitrite from the water
      • nitrosomonas: eat ammonia, convert it into nitrite
      • nitrospira or nitrobacter: eat nitrite, convert it into nitrate
      • grow best on filter media with a large surface area, e.g., bio balls, filter floss, sponges, ceramic noodles
    • denitrifying bacteria: remove nitrates from the water
      • exist where there is no oxygen present
      • when there is oxygen the bacteria use this to breathe instead of the nitrates, which is a process that converts nitrates into nitrogen gas
      • occur in places such as inside rocks
      • volcanic rock and ceramic noodles are suitable media for denitrifying bacteria
      • for freshwater tanks denitrifying bacteria is the least important type of bacteria, most people skip over it completely 
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Chemical Filtration

  • remove chemicals from the aquarium
    • including ammonia and nitrates
  • can also remove other pollutants such as: heavy metals, compounds (like sodium chloride), medication used to treat sick fish, tannins from driftwood that discolour the water
  • there are different types of chemical filtration
    • activated carbon which removes chlorine and chloramine, dissolved proteins, water discolouration, bad smells
    • zeolite is a natural volcanic rock that is made up mostly of silica and aluminium. It removes ammonia and is used in many freshwater aquariums.
    • oxide (aluminium oxide and iron oxide) is just rusted metal and removes phosphates. Aluminium oxide can increase aluminium levels in a saltwater aquarium so saltwater aquarium owners should use ferrous oxide instead
    • resin are used in water softening and purification. Man-made resins are made to remove specific chemical wastes such as phosphate and heavy metals. 
  • chemical filters are not unlimited resources, and when they are full, they can start releasing chemicals back into the water and won't absorb any more
  • some chemical filters need changing every few weeks and others every few months
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