In saltwater aquariums, there are three basic types of filters: mechanical, chemical and biological. Mechanical filters are the most popular filters because they’re less complicated and less expensive than biological and chemical filters. This doesn't necessarily mean that mechanical filters are the best. In fact, there isn't an overall winning filter. Rather, the best filter is determined by each aquarium’s individual needs.
Mechanical Filters
Mechanical filters remove solidified particles from the water column. These filters keep water clear, as well as remove organic materials before they have a chance to dissolve. If your system is fish-only, this filter has advantages of protecting your various pumps and catching debris. If you have a reef aquarium, a mechanical filter is unnecessary, especially if you’re also keeping crabs, shrimps or snails to clean the tank.
Chemical Filters
Chemical filters are best for removing dissolved substances from an aquarium. The tank’s living inhabitants are constantly releasing organic compounds. Once a compound has fully dissolved, a mechanical filter is no longer capable of removing it. As dissolved compounds fill a tank, the water will change color and appear murky, yellow or green. A chemical filter removes the dissolved unwanted compounds and returns the aquarium to its former clarity.
Biological Filters
Biological filters create nitrifying bacteria which convert the waste produced by your tank’s inhabitants to a nontoxic state. Biological filters, especially wet/dry filters, are the best option for an aquarium that doesn’t include live rock. The absence of live rock reduces the amount of surface area on which bacteria can grow, which in turn increases the amount of toxic ammonia. In this instance, a biological filter is the best choice because it’s capable of creating the bacteria needed to keep a saltwater tank balanced and livable.
Living Filters
Live rocks are extremely beneficial to a saltwater aquarium. Not only do reef aquariums provide fish with a more natural environment, they also add helpful organisms to the water, essentially making live rocks a natural biological filter. Scavengers such as snails and crabs are integral to the reef aquarium because they eat up solidified debris. You may never need to use a chemical filter if your aquarium houses the right amount of scavengers. These inhabitants are capable of eating up all the debris before it can break down and discolor the water. Living filters are always a great idea, but they should always be used in conjunction with a mechanical or biological filter.
References
- Advanced Aquarist: Advanced Beginnings: The Basics of Filtration for the Reef Aquarium
- The Reef Tank: Blog: Setting Up Your Saltwater Aquarium
- Aquarium Connection: The Ultimate 20-30 Gallon Reef Tank: Filtration
- Rate My Fish Tank: Saltwater Aquarium Filtration
- Aquatic Connection: Reef Aquarium Refugiums
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