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Thread: PFK Articles: Tetra tutorial: Filters

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    Feed Icon PFK Articles: Tetra tutorial: Filters

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    Rupert Bridges of Tetra explains how filters work.

    "Filter: An apparatus for purifying a fluid of solid matter by pouring it through porous media…"

    The dictionary definition of a filter doesn't even begin to describe the piece of kit that virtually every fishkeeper uses in their aquarium these days.

    The modern filter will remove solids from the water, but this is far from the most important part of its function.

    The media within a filter is invariably made of a porous material that can sieve out solids, but it also makes a very effective home for the aerobic bacteria (oxygen using bacteria) that break down the ammonia and nitrite that is produced by fish excretion and uneaten food and other wastes breaking down in the aquarium.

    This media eventually blocks and needs cleaning, but it should never be washed in anything but old aquarium water as chlorinated water will kill the friendly bacteria.

    Filters also supply water movement – internal filters can be set up and aimed down the aquarium to supply natural movement for those fish that like river-like currents.

    In addition, many of the internal filters aid aeration with venturi units, while the returns from external filters can be splashed onto the water surface of the aquarium to break the surface and aid gas exchange and aeration.


    Friendly bacteria
    Ammonia is a killer. Any waste food, decaying organic matter, dead fish or rotting plants will produce more ammonia. Several bacterial species can oxidise ammonia to much safer nitrate, the best known being Nitrosomonas, Nitrospira, and Nitrosospira.

    But for aerobic bacteria breaking ammonia down as they use up oxygen, the earth – let alone your tank – would not support life.

    These bacteria like plenty of surfaces to cling to, hence the need for porous filter media which has a high surface area.

    Once these sessile bacteria have locked themselves in place on a suitable surface, they need a constant flow over them, bringing oxygen and food in the shape of ammonia.

    It's therefore essential that the media doesn't become blocked, stopping the water flow over the media, and that your tank is well oxygenated – approximately 4.3 mg of oxygen is consumed for every mg of ammonia broken down to nitrate.

    Some filters, such as the TetraTec EX externals, feature pre-filter media, extracting the solid wastes before they can clog the main biological media, ensuring a flow of well-oxygenated water.


    Modern filters
    Internal filters are effective tools that will complete the so-called ammonia cycle in your aquarium. TetraTec IN plus filters work both biologically and mechanically.

    The media will remove solid wastes. In the process, the friendly bacteria that find the media an ideal environment break down dissolved ammonia and nitrite, keeping the aquarium suitable for fish.

    Most internal filters can, like TetraTec IN filters, be set up to re-oxygenate water as it is re-circulated, further improving conditions. The IN Plus units can be lifted out for easy cleaning, which encourages you to keep the media open and free of blockages.

    Internal filters sit inside the aquarium and are a little limited in size. Two internal filters (or arguably three or four) could be used in a large aquarium, and will promote excellent surface flow and attractive currents for riverine species.

    In addition, Tetra's units have a venturi feature, which will aerate the water.

    External filters will hold larger amounts of media than internal filters, which help create a healthier, cleaner environment in larger or heavily-stocked tanks. They are easier to maintain because all working parts are outside the aquarium.

    You can buy different types of media to filter chemically (carbon, zeolite), to change the water chemistry (calcium chips) or to increase the removal of solid wastes (filter floss).

    Between the two types of filter, it should be possible to filter almost any aquarium. Internal filters are at their best when used to filter smaller, lightly stocked aquaria, with externals more at home on large or heavily stocked tanks.

    How do I ensure that my filter works biologically?
    Good question. All filters need to mature and build up a head of friendly bacteria before they will break down ammonia and nitrite.

    This can be done in several ways, but Tetra offer a fast, efficient solution in the shape of TetraAqua SafeStart. This liquid treatment quickly establishes a biological environment which can allow immediate introduction of fish into a newly set-up aquarium.

    SafeStart contains the living Nitrospira, Nitrosospira and Nitrosomonas bacteria that can safely reduce toxic ammonia and nitrite in aquariums.

    Obviously this is extremely useful when setting up a new aquarium, but other factors such as remedies used in the aquarium, de-oxygenation problems, power cuts and filter maintenance can deplete the bacteria, so it can be used regularly to boost filtration.

    SafeStart keeps for 12 months with no refrigeration between 2°C and 30°C. Use with AquaSafe to neutralise chlorine before it damages bacteria in the filter.


    What maintenance is necessary?
    Most filter media clogs eventually, and as chemical media work by adsorption – taking and fixing chemicals to their surfaces – they eventually need discarding (carbon) or in some cases re-charging (zeolite).

    Clogged filter media may have to be changed, or if less dirty, washed in aquarium water to remove mulm. Wash media before it gets too dirty.
    To ensure that bacterial colonies aren't permanently damaged, wash or change only the half the media at a time.

    On the TetraTec IN filter, the filter sponge is split into two segments. In this way, one can be replaced while the other maintains a population of beneficial bacteria.

    Wash or replace one sponge at a time, rinsing it in a bowl of aquarium water and never under the tap. And don't use soap!


    Shopping list
    AquaSafe conditions the water and removes chlorine, making it safe for filter bacteria; SafeStart speeds up the filter maturation process.

    TetraTec EX external filters for filtering larger or heavily stocked aquariums. There are three models: 600 for 60-120 l aquaria; 700 for a 250 l aquaria, and 1200 for aquaria from 200-500 l.

    The TetraTec IN Plus aquarium filters are internal filters for biological and mechanical filtration, with an optional activated carbon sponge for chemical filtration and a venturi feature to re-oxygenate the water as it is re-circulated and an adjustable flow.

    The filters have a two-year guarantee. They come in the following models: 400 for a 30-60 l aquarium; 600 for 50-100 l; 800 for 80-150 l; 1000 for a 120-200 l set-up.

    The Tetratec Easy Crystal Filter supplied with the Tetra AquaArt tank comes with a one-touch replacement cartridge system, which can be accessed without removing the filter.

    The cartridge polishes the water and the carbon removes impurities before a biological media element keeps ammonia and nitrite under control.
    Complete article here.

    * This thread is an item from Practical Fishkeeping Magazine website's Articles RSS feed, brought to you by courtesy of AQ's RSS Feed Poster Robot. *
    Last edited by benny; 5th Jul 2007 at 10:27.

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