Aquarium Filter Information

A q u a r i u m F i l t r a t i o n

In an enclosed environment, the water chemistry is ever-changing and as a result the environment has an affinity to continually change with it. Unfortunately most fish and invertebrates have limitations on their ability to cope with these changes. This is why it is preferable to come as close to duplicating the natural habitat as possible. A sound and functional filtration system is the one of the key elements to achieving this. There are many options available, and a huge variety of filters to choose from. Educate yourself or consult with us to determine which filtration system is best for your aquarium. Filtration systems that are easily accessible for maintenance are preferable. This series of pages is designed to offer information about the different devices available, and how they work in this end of aquarium keeping.



The three vital types of filtration to an aquarium are biological, mechanical, and chemical. Simply put, biological filters encourage the growth of nitrifying bacteria that breakdown ammonia to less toxic chemicals such as nitrate. Mechanical filters aid in the physical removal of waste products, and debris (detritus) from the aquarium. Chemical filters purify the water by chemical reactions that take place at the cellular, microbial, and even atomic levels. In most cases, it is best to incorporate all three types for optimum results. In certain types of aquaria, these are the minimum filtration requirements. In other types, only one may be used as the primary filtration mechanism. Below are links to pages that go into more thorough detail about the different types of aquarium filtration:

Biological Filtration

Fluidized Bed Filtration The successful aquarium is virtually a living ecosystem. A part of the ecosystem involves microorganisms and chemical reactions. A sound biological filter is considered by many, the most important filtration system of the aquarium ecosystem. A biological filter is one that involves the propagation and retention of billions of aerobic and anaerobic bacteria. Most aquarists pay close attention to the aerobic, or nitrifying bacteria (Nitrosomonas, Nitrobacter). These bacteria grow in the presence of oxygenated water with a food source such as ammonia (NH3), or nitrite (NO2) present.

Initially, the sound of growing bacteria, and creating a biologically active ecosystem sounds like a complicated process, but it actually is fairly simple with the right conditions, equipment, and animals.

Most commonly, the bacteria are added by simply adding fish. They hitch a ride on the very bodies, mouths, and gills of fish and other living organisms. They will drop off the bodies of the fish, and spread throughout the aquarium. Anywhere there is oxygen-rich water, these bacteria will grow. The only problem with this process, is that fish also produce ammonia. In fact, more than the bacteria to compensate for its own waste. So fish need to be added gradually, because these bacteria can take several months to fully establish.

These nitrifying bacteria consume ammonia (NH3) and nitrite (NO2) to break these common toxic aquarium chemicals into nitrate (NO3), the final bi-product. NO3 is then removed either by further chemical processes, or more commonly, by changing out a percentage of the total aquarium water on a regular basis, and replacing with water that is free of heavy metals, and is the appropriate temperature, pH, and hardness (and salinity in the case of marine tanks.)

There are many types of biological filters out there today, many of which also incorporate other types of filtration. Some commonly used bio filters include: under gravel filters, bio wheels, trickle filters, canister filters, fluidized bed filters, sponge filters, and live rock/live sand have also become popular in saltwater reef aquaria.

Every aquarium is a different environment, and has has it's own set of demands. Some filters are better suited for a some aquariums then others. Consult us, or read up on what biological filtration is right for your aquarium system.

Chemical Filtration

Chemical filters are commonly used in aquaria applications, and for good reasons. This is a good way to keep the water very pure and crystal clear. Chemical filters are not used in all applications, as most are with biological and mechanical filters.

As with the other types of filters, the choices of devices in chemical filters are many. The proper choice here is key, and can directly affect the short, and long term health of the specimens. Consult with an expert, or read up on what system is appropriate for your aquarium.

There are different methods to "chemically" treat the water. Some of these ways include: ion exchange, adsorption, chemical bonding, and molecular destruction. There are many different media that you can use in the chemical filter, and in different applications. Some of these chemicals include: carbon, zeolite, peat moss, calcium hydroxide, poly adsorption pads, and other chemically treated media. There are also many other additives, and vitamins to aid in supplementing the efficacy of the chemical filtration.

These are some of the most commonly used chemical filters on the market today.

Canister Filter-These are available in both free-standing and hang-on units. Water is taken from the aquarium via the water pump in the filter. Media is used in the canister such as carbon, or zeolite. Many times, mechanical medium, or sometimes even biological medium is incorporated into the canister to make it multi-functional.

Trickle Filter-Popular among reef hobbyists, and other serious aquarists, the trickle filter is the ultimate in combining many types of filters, including chemical. There are many interesting designs. Most are a separate system, whereby water is drawn from the aquarium, siphoned through the mechanical, biological, chemical, and auxiliary filters, and put back into the display tank. Trickle filters offer great filtering diversity because of the physical size, and the fact that the filter is a separate entity from the display tank.

Power Filter-Most are available in hang-on units that simply mount to the back of the tank. These have fairly simple designs, and few moving parts. They are also inexpensive.

Reactor-Water is pumped through a canister-type chamber, and exposed to the chemical media. Sometimes these reactors are run pressurized for more effective filtration. Reactors are good for targeting specific chemicals to remove from the system water.

Internal Filter-Effective, simple, and inexpensive. These filters are small, and go into to display tank, or sump. Many people use these in smaller aquarium applications.

Chemical Additives-Can be effectively used to remove toxic elements such as ammonia, nitrogen compounds, and heavy metals to ultimately purity the water to the desired specs. These are available in many different types and sizes.

Foam Fractionization-Also referred to as protein foam skimming. Used primarily in saltwater applications, but infrequently also effectively used in freshwater tanks. Usually, these filters are tall and columnar in shape. The principle is to pump water and tiny air bubbles into the column. This air/water contact time allows the toxins to bind to the tiny air bubble and form a scummy foam. This foam contains many bad, (and sometimes good) elements from the aquarium water. Also considered an auxiliary filtration device. Protein Skimming is an efficient form of toxin removal.

Mechanical Filtration The principle behind mechanical filtration is simple. The idea is to physically remove particles, and waste matter from the aquarium water. Many times a fine medium such as cotton, dacron, and other synthetic materials are used to trap detritus, dead plant matter, and other debris. Mechanical filters need to be removed, cleaned, and replaced on a regular basis. Otherwise, waste products will accumulate, and decompose, continuing to lower the livability of the aquarium environment. This puts major stress on the fish and other inhabitants of the aquarium. One of the secrets to successful aquarium care in all applications is to maintain the mechanical filters. Replacing this media will help ensure the long term success of the tank.

Proper flow rates through mechanical media is key to the proper filtration of the total aquarium water body. Flow that is too slow, or too fast will impede the filtering capacity. Most filters flow rates are set at the manufacturer, but many times unchanged filters will lead to diminished flow, and ultimately stagnant water.

These filtration devices come in many forms, and offer a diversity of media. As with the other types of filtration, combining mechanical removal with other forms of chemical, biological, and auxiliary filters can prove to be very effective. In combination systems like this, the mechanical filters are often found first. In many aquaria applications, it's beneficial to physically remove debris, before passing the water over finer filtering devices. Some systems even post-mechanically filter the water over a very fine medium to provide a "polishing" touch to the tank water.

Mechanical media can be used in most all filtration devices, making this the most versatile type of filter available. Virtually all filters can hold a form of mechanical medium, so we will not list all of the filters available. However we will name off a few, and these include:

Power Filter-Also commonly used as chemical/biological filtering devices. These self enclosed units are quiet, energy efficient, and easy to maintain.

Canister Filter-Most are run by their own pump, and have large filtering capacity. Lots of mechanical medium can fit into many of the different canisters available.

Internal Filter-These run within the aquarium, and are either powered by an air pump, or small water pump. Internal filters are simple in design, and easy to operate. They work very well in smaller aquaria applications, and are a great way to supplement large aquarium applications.

Diatom Filter-Similar to a canister filter in design. The diatom filter passes water through fine diatomaceous earth powder. This filter is the ultimate in mechanical polishing filters. Most can remove debris of particle size down to 3 microns. May, in fact, over-filter the water, and take out beneficial elements from the aquarium water. Many aquarists use this filter in temporary applications, or as a maintenance tool.

Wet/Dry Filter-Some of these units have multiple mechanical filtering compartments for using multiple filtrant media. Often, pre-filter devices mechanically filter the water before passing it on to the other chambers in this filter.

Auxiliary Filtration





Carbon Dioxide System-These allow the precision aquarist an advantage by being able to regulate carbon dioxide (CO2) levels in the aquarium. This directly affects the buffering system, and allows the aquarist to regulate aquarium parameters such as pH.



Ultraviolet Sterilizer-Very effective filtration devices for purifying the water, and keeping it bacteria and parasite-free. Water is passed through a tubular filter body., which is then exposed to ultraviolet light. This filter kills a variety of free floating fungi, bacteria, and protozoan. The bulbs have a life of about a year. Filter efficacy greatly diminishes with the age of the bulb.



Reverse Osmosis -And other water purifying filters are used by aquarists who have very high demands for water quality. These filters supply a convenient, and constant water supply, and can be hooked up to most aquariums, and filters via a float valve. Some RO filters like this one pictured also have an optional deionizing filter for reef applications.



Foam Fractionization-Also referred to as protein foam skimming. Used primarily in saltwater applications, but infrequently also effectively used in freshwater applications. Usually, these filters are tall and columnar in shape. The principle here is to pump water and tiny air bubbles into the column. This air/water contact time allows the toxins to bind to the unstable oxygen molecules, and form a scummy foam. This foam contains many bad, (and sometimes good) elements from the aquarium water. Also considered a chemical filtration device. Protein Skimming is an efficient form of toxin removal, and a must for most reef tanks.