Filtration and aeration

Filtration

To ensure the removal of debris from the water and to assist the breakdown of harmful waste, an effective filtering system is required. There are basically two types of filter systems that have been proved effective and trouble-free for the tropical fish keeper. These are the undergravel 'biological' filter and the mechanical filter.

The undergravel filter

has proved to be simple and reliable in small and medium sized tanks, particularly where the number of fish kept is small. It comprises a perforated plastic plate that sits on small projections which hold it about a 1/2 inch (13mm) off the aquarium bottom. An air lift or powerhead connected to this plate via a plastic tube, causes water to be drawn from beneath it and fresh water to be drawn through the plate and covering gravel to replace it. This flow of water draws with it any suspended matter in the water, depositing it in the gravel where it is quickly broken down by a bacterial process in to harmless chemicals. The grain size and depth of the material covering the filter is important. It should be about 1/8 inch in size and have a depth of about 2 inches (5cm), with an optimum depth of 3 inches (7.5cm). One of the disadvantages of the undergravel filter is that it will need cleaning when it becomes choked. This may only need to be done after a year, or even two years, in a tank with only a few fish in it. The filter should cover at least 2/3 of the tank base if it is to operate with maximum efficiency.

Mechanical filtration

involves passing the water through a nylon medium that traps all the solid waste matter. Once a week, or more often if necessary, you must remove the filter from the aquarium and wash out the nylon medium (replace if necessary) and any mechanical parts of the filter.

There are many different designs of mechanical filter, some being small rectangular boxes that sit on the floor of the aquarium (bottom filters), others clipping to the outside of the aquarium where they do not interfere with the display that you have created. Usually they are air operated, but the most powerful ones incorporate motorized water pumps; these are generally known as power filters, and are especially useful on aquaria 36 inch (90cm) long or larger.

Aeration

Although a certain amount of aeration is provided by the operation of the filter, there is much to recommend the use of an air pump to provide streams of fine bubbles to help stir the water even further. It is certain that vigorous aeration is helpful to the well-being of fish and aids the dispersal of carbon dioxide which might prevent the saturation of water with oxygen.

Air pump

A strong, powerful air pump is needed to operate an airstone and an aeration filter. If both units are to operate from one pump it is better to purchase one which has two outlets. Although, it may be better to use two separate pumps, then if one should fail, the other can take over until a replacement is obtained.