Aquatics - Filter Types


Under Gravel: How does it work?

  • internal
  • mechanical and biological
  • plate is covered in gravel
    • the plate is plastic mesh type
  • pulls water down through a media base that sits on top of a plate that traps particles in the media as water passes through it
  • run by an air pump and air stones
    • some types can be used with a powerhead
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Under Gravel: Pros and Cons

  • Positives
    • traps debris in gravel and not the water
    • filters the water
    • water flow constant
    • easy/simple
    • reliable
  • Disadvantages
    • best used in tanks under 55 gallons or 250 litres
    • not appropriate for reef tanks
    • not really effective
    • high nitrate levels if not cleaned properly
      • due to the accumulation of detritus and other organic matter
    • dead spots can form under the plate
      • allows the growth of unwanted bacteria
      • contribute to poor water quality in the long run
    • require regular maintenance
    • cannot be used with fish that dig
    • export of waste is more difficult
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Foam: How does it work?

  • removes particles from the water
  • external and internal
  • mechanical
  • allows water to pass through foam/sponge
    • removes physical objects
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Foam: Pros and Cons

  • Positives
    • helps prevent filters and tanks getting clogged
    • stabilises pH levels
    • helps prevent algae build up
    • easy to clean
    • can provide a home for beneficial bacteria
  • Negatives
    • removes beneficial bacteria from tank
    • removes trace elements
    • relatively expensive
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Power: How does it work? Part 1

  • chemical, biological and mechanical depending on media used
    • make poor chemical filters and adequate biological filters
  • internal
  • also called hanging filters or overflow filters
  • sold with inexpensive aquarium kits
  • any filter that hands off the back of the tank and draws water in through a lift tube and returns it through a spill-way
  • any hanging filters with a water pump to move the water
  • 1. draw water up a lift tube
  • 2. water is pushed through a series of filter media (bottom-to-top and back-to-front. depending on the filter model)
  • 3. after the water has gone through the media, it flows over a spill-way or overrflow and back into the tank
  • 4. water is moved by a water pump which pulls water through the lift tube or by air bubbles (From an air pump)
    • lift water into the lift tube and over into the filter box
  • maintenance requirement vary
    • dependent of filter brand, filter model and type of media
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Power: How does it work? Part 2

  • many power filter suse manufactured filter cartridges that fit a specific model
    • can be rinsed out when you do water changes to remove accumulated debris
    • need to be replaced frequently
  • sponges used in power filters should not need to be replaced until they deteriorate.
    • just rinse thoroughly in dirty aquarium water as necessary
  • carbon or zeolite cartridges should be replaced frequently to preven the release of toxins into the water
  • remove any carbon from the tank or filter before you medicate
    • if carbon is working, it should remove the medication in the tank within an hour, which won't be enough time for the fish to be treated
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Power: Pros and Cons

  • Positives
    • increase the surface area will improve dissolved gas levels
    • make good particulate filters
      • can be set up as poor chemical filters or adequate biological filters
  • Negatives
    • can be inefficient
      • have their intake directly below the spill-way
        • a significant portion of the water drawn into the filter for cleaning is water that has just been returned from the filter
    • can lose water
      • when the water is returned to the tank the surface area is increased and evaporation occurs
    • evaporation encouraged due to the large area cut out of the top of the filter
    • cut out can provide an escape for jumping fish or amphibians or crustaceans
    • have to remove most of your biological bacteria bed when filter cartridge is replaced
      • causes the tank to cycle again
      • make sure you get one with multiple pieces of filter media or has some permanent filter media attached or built in
    • need to be replaced frequently
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UV Steriliser: How does it work?

  • internal
  • external: sits on the side of the tank
  • mechanical
  • works in marine and freshwater
  • acts as a prophylactic (disease preventer)
  • clearer water
  • a tube of UV light that kills single cell organisms that go through it by altering and damaging their DNA
    • as the light penetrates the bacteria/algae it mutates the DNA which prevents growth/multiplication
  • in and out flow
  • utilises a germicidal fluorescent lamp that produces light at a wavelength at approximately 254 nanometres
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UV Steriliser: Pros and Cons

  • Positives
    • Convenient 
    • No chemicals
      • non-toxic
      • environmentally friendly
    • kills all kinds of microorganisms, including drug resistant bacteria
    • can act as a light
  • Negatives
    • UV dangerous to humans and therefore difficult to manage
      • avoid exposure to skin and eyes
    • can be blocked by objects
    • multiple UV bulbs needed to access all areas
    • expensive
    • needs replacing: if it runs out it is less effective
    • can't be used when medication is added to the tank
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Activated Carbon: How does it work?

  • internal
  • chemical
  • used to purify liquids and gases
  • removes many organic and inorganic materials dissolved in the tank
  • clears water and removes odour
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Activated Carbon: Pros and Cons

  • Positives
    • low cost
    • easy maintenance
    • can absorb leftover medication within the water
  • Negatives
    • short life span
      • hard to know when it needs replacing
    • when they are full, the run the risk of leaking chemicals they've collected back into the water
    • does not remove important toxins, such as ammonia, nitrite and nitrate
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Ozone: How does it work?

  • chemical
  • external
  • generator charges oxygen to create ozone
    • ozone is an oxidiser
  • ozone generators apply an electrical charge to the air that passes through
  • splits apart normal oxygen atoms into unstable single atoms
    • Bond with other Omolecules to form O3
  • Used in residential and commercial filtration
  • ozone attacks and neutralises contaminants and then reverts back to oxygen
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Ozone: Pros and Cons

  • Advantages
    • saves time and money
    • some able to eliminate the need to use unwanted additional chemicals (e.g., chlorine)
    • sterilising qualities
    • can remove clouding or colouring of the water
    • destroys toxins
    • gets rid of tank odours
  • Disadvantages
    • expensive
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Foam Fractionation: How does it work?

  • a chemical process in which hydrophobic molecules are preferentially separated from a liquid solution using rising columns of foam
  • used for the removal of organic waste from aquariums
  • known as protein skimmers
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Foam Fractionation: Pros and Cons

  • Positives
    • removal of suspended solids
    • removal of proteins and high molecular weight compounds
    • increased water clarity through the removal of humic acid phenolic compounds
    • increased oxygenation of the culture water
    • pH stabilisation through removal or organic acids
    • good for reef aquariums
  • Negatives
    • performance dependent on:
      • air to water ratio
      • air bubble diameter
      • column height
      • air/water contact time
      • use of ozone
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