Goldfish Water Filters and Air Pumps
To achieve good clean water, you need to have some sort of filtration system in your goldfish aquarium. The water is cycled through a filter that utilizes one or more of these filtration techniques:
Mechanical filtration - foam or a similar material, removes any large particles such as bits and pieces of food decaying plants.
Chemical filtration - plates of active carbon and other substances are used in many filters to absorb ammonia and other harmful substances from the water.
Biological filtration - bacteria that builds on the surface of the filter helps break ammonia and its products into harmless nitrates. The beneficial bacteria can live almost anywhere in your goldfish aquarium, but many water filters intentionally provide space for the bacteria to grow inside. You may want to read more about the nitrogen cycle in setting up your goldfish aquarium.
There are several types of filters available, defined by their position in the goldfish tank. For the goldfish beginner, starting with a small to average sized aquarium, the best setting is an undergravel filter, combined with a power filter (either external or places within the water tank). The undergravel filter is placed at the bottom of the aquarium, underneath the gravel, with one or two tubes linking them to the top of the tank, circulating the tank water, as well as air, through the system. This type of filter lets in a lot of oxygen into the gravel bedding itself, thus contributing to the growth of beneficial bacteria. Combining a power filter adds chemical and mechanical filtration.
No matter which filter you are using, it's imperative that you have some sort of air pumps constantly pumping air into the water. Aeration provides oxygen for the fish, as well as for the beneficial bacteria that is so vital to them. Many water filters provide aeration by creating bubbles on the surface of the water. This is usually sufficient for a small to middle sized goldfish aquarium. Larger tanks require additional air pumps and air stones, but it never hurts to add them even in the smaller goldfish tank. Make sure that you have some sort of aeration system in your goldfish aquarium!
Refer to the other pages in this section for more information about choosing the right goldfish aquarium, heating and lighting, water plants and gravel and decorations.