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Aquatic Fantasy Blog

How Does Saltwater Aquarium Filtration Work?

Posted on June 28, 2015

Learn about the three main filtration processes for a saltwater aquarium.

How Does Saltwater Aquarium Filtration Work?When setting up a saltwater aquarium, most people are more excited about picking out their fish, corals, and invertebrates than setting up their aquarium equipment. But of course, having the right equipment is absolutely essential to keeping you aquarium residents happy and healthy.

Filtration is probably one of the most important aspects of aquarium setup for a new hobbyist to understand. The topic can seem overwhelming, but once you understand the basics you will be much better equipped to pick out the right filtration system for your new aquarium.

Three Types of Filtration Processes

Keeping your aquarium water clean is about much more than just removing floating debris. It also requires removing chemicals that would be harmful to your fish in high concentrations. To achieve this dual function, more than one type of filtration may be needed. Here are the three main ones.


Biological filtration is the most important type of filtration in any saltwater aquarium. This is a natural process in which beneficial bacteria convert the various waste products generated by your fish into a harmless state. Most importantly, the bacteria will prevent ammonia from building up. Ammonia is a byproduct of fish breathing, so allowing ammonia to accumulate in your aquarium is the equivalent of allowing carbon dioxide to build up in your home—a very bad idea.

There are two main ways to incorporate biological filtration into your aquarium. First, you can simply purchase a biological filter such as an undergravel filter, a bio-wheel, wet/dry filter, or trickle filter that will give the good bacteria a place to grow. Alternatively, you can add live rock or sand to your aquarium. This is actually a better option because it provides the bacteria more surface area to grow.


Mechanical filtration can be used to remove particles that would otherwise float around in the water and make your aquarium look cloudy. Removing this debris quickly also prevents it from having a chance to break down into harmful compounds that will throw off your aquarium chemistry.

The most common type of mechanical filter is just a simple powerfilter with floss pad inserts. However, if you have plenty of invertebrates eating up the debris in your aquarium, you may not need to purchase a mechanical filter because they will fulfill this role for you.


Chemical filtration is a non-biological means of removing waste that has already dissolved into the aquarium water, aka Dissolved Organic Compounds. Chemical filtration prevents DOCs from building up to the point where the water takes on a yellow tinge.

The most common type of chemical filtration involves using a filter packed with activated carbon to absorb the DOCs. Other tools that fall into the category of chemical filtration include protein skimmers, ozone filters, and UV sterilization filters.

So What Type of Filter Should You Choose?

Your best bet is to pick a filter that incorporates all three means of filtration, such as a power filter (for tanks up to 55 gallons) or a canister filter (for tanks up to 250 gallons). Note, however that canister filters require the addition of an aerator to ensure there is enough oxygen in the water.

If you would like help picking out your saltwater aquarium filter, please give us a call at 310-798-7333 or stop by our store to talk about your needs.


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