Aquarium Filters
Good quality aquarium filters are among the required items for all fresh or saltwater tanks (with the exception of the humble goldfish bowl). While there are many kinds of filters for both fresh and saltwater, one of the most common is the under-gravel or under aquarium filters. It works by creating a large surface area for de-nitrifying bacteria to colonize out of the substrate itself.
Filtration Basics
All filters primarily work by creating a large surface area for beneficial bacteria to colonize. This allows them to process the excess nitrogen in the water and populate so effectively as to discourage any antagonistic bacteria or water fungus. The mechanical motion of the water and the introduction of bubbles into the system is also beneficial in maintaining a reasonable and healthful mixture of solutes and gasses in solution.
One must be very careful not to overload the system with fish or nitrogenous matter. New saltwater tanks that haven't had time to fully colonize with beneficial bacteria are far more prone to filtration issues that well-established tanks.
Types of Filters
Among the most common are under gravel filters; this is most likely due to their low cost and ease of assembly – in fact they are the most commonly made DIY aquarium filters. However, they are tedious to maintain and will eventually fail, even in limited use.
Other biological filters include live sand, wet-dry trickle filters, and granular activated carbon. Other types are either mechanical or chemical, including canister
filters, protein skimmers and mangrove plants.
Generally mechanical and chemical filters will hang on the tank or be located remotely, usually next to the tank.
Choosing the Best One
First you'll need to decide if you want to use a sump pump. Very commonly used with equipment suitable for reef aquarium filters, they can be noisy and might leak outside the tank. You will, however, have a lot more oxygen to work with, allowing you to keep a wider variety of species. If you don't want the bother, you'll be limited in the types of creatures and how many you can put in a given tank.
Most types of filters have a version that hangs on the tank or resides outside, and many combine methods of filtration. You'll want to consider just how you want the tank to look and the marine creatures you want to put in it; some have much stricter requirements for an aquarium filter than others.
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