When it comes to keeping tropical fish, water quality is all important. There are a number of factors which will affect the quality of the water in your corner aquarium but one of the most important is the quantity of ammonia present in the water. Ammonia is a highly toxic waste product produced by the kidneys of fish and excreted into the water. In the wild, fish generally live in relatively vast quantities of water and the ammonia is quickly diluted so that unless the water is otherwise polluted it never reaches dangerous concentrations.
In the corner aquarium however there is far less water to perform this function and if the tank is not properly maintained ammonia can become sufficiently concentrated to harm the fish. This potential threat can be removed by the use of beneficial bacteria contained within a suitable tank filter which convert the ammonia into less toxic substances.
Filters can be contained within the aquarium (an "internal" filter) or outside (an "external" filter). Although some aquarists (ourselves included) have a preference for one type over the other either will do the job well. The most important feature is that the filter should contain a material with a very large surface area e.g. synthetic cotton wool or ceramic noodles which have space for the many millions of bacteria required to break down the ammonia and other waste products.
Such bacterial filtration is however only one element of aquarium filtration. An aquarium filter also needs to provide mechanical and chemical filtration.
Mechanical filtration is relatively straightforward. As part of the normal operation of the corner aquarium detritus will collect in the water; fish waste, fragments of plant, uneaten food and the like. This needs to be removed both to maintain an attractive aquascape and to reduce the likelihood of decomposing matter polluting the water. This is normally achieved by including in the filter a means of physically removing the offending items from the water. In modern filters this is usually by means of a foam pad.
Chemical filtration is a little more complex. In addtion to ammonia many other chemicals that can't be removed by mechanical or bacterial methods accumulate in aquarium water over time. Some of these are indigenous to the aquarium; particles and nutrients from fish waste, proteins, hormones and such like. Others invade the aquarium water from the surrounding atmosphere; pesticides, air fresheners, cooking odours, cleaners and the myriad of other chemicals and substances which circulate in varying quantities in the modern household.
To remove these a substance known as activated carbon is used. In very simple terms, this comprises carbon which has been heat treated to produce millions of tiny pores. These give each fragment an enormous surface area with which to absorb undesirable chemicals from water passed through it. It is invaluable in the aquarium filter and if properly maintained can result in crystal clear "invisible" aquarium water - the goal of every aquarist. Because it absorbs impurities so efficiently the activated carbon becomes clogged up and requires to be changed at regular intervals, usually three to four weeks, as part of normal aquarium maintenance.
Corner Aquarium Filters
With just a few exceptions, all the corner aquariums available online in the UK today are supplied with suitable filtration, either internal or external. Each is adequate for the job although as you will know if you have read the feature on Corner Aquariums Compared we do have a slight preference for the external filter on the basis of its minimal intrusion into the aquarium and (we think) easier access for routine maintenance.
Having said this one of the most popular corner aquariums in the UK today, the Juwel Trigon 190 comes supplied with an internal filter and this doesn't appear to have put buyers off in any way. The internal filter does have the advantage of producing a corner aquarium which is wholly self contained and this has its appeal. In addition it removes the risk of leaks which is present, at least in theory, in the case of external filters.
Below are details of the filters supplied with the corner aquariums available today along with those we'd recommend purchasing where none is supplied.