There exists a wide range of different aquarium equipment in the aquarium trade, and knowing what to buy can be difficult. The subject of filtration is certainly no exception, and when you visit an aquarium shop you can usually find a vast array of various filtration equipments; from comparatively inexpensive sponge filters to pricy protein skimmers. Different types of aquarium will require different types of filtration, and your experience as an aquarist can also affect which type of filter that is ideal for you.

Another important question that you must ask your self is how much time and money you are prepared to spend, and how noise tolerant you and your family are. Do you have time to clean your filter very often, or do you need a filter system that pretty much take care of it self? Is it very important to you that the filter is silent, or is it okay to have a noisy filter system if you can save some money? You might be able to accept one type of filter for the aquarium in your garage, while a much more silent filter is necessary for the aquarium that you keep in your bed room.

By researching the various filter types before you start shopping for a filter, it will be much easier for you to determine what is best for your particular fish species, aquarium size and budget. This way, the risk of being lured in to purchasing a superfluous filter system will be decreased. The risk of getting a really cheap and low quality filter system that you are forced to replace after just a few months will also decrease.

As mentioned above, different aquariums will need different types of filtration. There is for instance a big difference between a saltwater aquarium and a freshwater aquarium. Not only are marine fish species typically more sensitive to poor water quality; the basic water chemistry in a saltwater aquarium is also different which means that other forms of filtration can be used, e.g. the popular protein skimmer. A small aquarium will also typically need more powerful filtration than a medium sized or large aquarium, since the water mass is very small and therefore not capable of diluting a lot of waste products.

Recommending a filter that is ideal for any aquarium regardless of size, flora and fauna, water chemistry etcetera is naturally impossible. It is therefore also impossible to answer general questions such as "How much should a filter cost for my first aquarium?" or "Do I have to get a protein skimmer for my saltwater aquarium?" Certain types of aquariums can even be kept using biological filtration only - mechanical and chemical filters are not mandatory in successful aquarium keeping. You can also lower the need for mechanical filtration by not keeping messy eaters, by removing any free floating debris by hand, by devoting time and effort to the development of a properly functioning semi-ecosystem, and by never overfeeding your fish or leaving left over food in the water. An aquarium is too small to form a perfectly balanced ecosystem, and you are constantly adding nutrition from outside the system, but you can obtain a form of semi-ecosystem that only requires biological filtration and regular water changes to function. Such a system is however delicate, and for the novice aquarist or the keeper of sensitive species, a combination of biological, mechanical and chemical filtration is usually necessary.