Learn about the different types of filters for your freshwater aquarium.
Setting up an aquarium involves purchasing and installing a variety of pieces of equipment. Perhaps the most important piece of equipment for your entire aquarium, however, is your filtration system. Filters are essential for maintaining a clean and healthy environment for your fish which, in turn, is essential for keeping your fish healthy themselves. Without a filtration system for your water, it would almost be impossible to keep tropical fish as a pet. Filtration systems are that important!
Choosing a filtration system can be a daunting task because the sheer number of options to choose from can be overwhelming and become confusing. The fact that choosing the right filtration system is so important may also make the task more challenging – you certainly don’t want to make the wrong choice! Before you select a filter, take the time to review your options and think about the specific needs of your tank. You should also take some time to learn about the different types of filtration that come into play in choosing an aquarium filter.
Types of Filtration
Mechanical Filtration – This filtration process simply removes debris and particles present in your water by passing the tank’s water through foam or some other type of spongy material which traps the debris from entering back into your tank. The foam is replaced on a regular basis to prevent back-up and to maintain the effectiveness of your filtering system
Biological Filtration – This is the most important filtration process for your aquarium. Though it doesn’t actually involve filtering anything out of your tank water, this type of filtration does make it possible for toxins and dangerous chemicals to be removed from the tank. Biological filtration involves cultivating a colony of beneficial bacteria which establish and then maintain the nitrogen cycle – the cycle through which ammonia (the product of waste breakdown) is converted into less harmful substances which can then be removed from the tank through water changes. To learn more about the nitrogen cycle and how it affects your tank, read RateMyFishtank.com’s article on cycling your tank.
Chemical Filtration – This filtration process removes dissolved wastes by flowing water through activated carbon. Activated carbon is extremely porous and when water flows by, it the pores trap dissolved wastes and minerals such as phosphate. Activated carbon can also remove odors and ammonia from tank water. Though your tank may be able to get by without chemical filtration, you will need to perform very frequent water changes to maintain high water quality in your tank. Having chemical filtration in your tank is not only a much easier, but also a much more efficient option.
Almost all filtration systems will utilize mechanical and biological filtration processes and most of them will allow you to add a chemical filtration unit. Choosing the right filtration system for your aquarium usually depends on the size of your aquarium, the size of your budget and the specific filtration needs of your fish and plants. The following list contains most of the standard filtration systems found in pet supply stores and goes into the pros and cons of each. Take a look at your specific needs for your aquarium and use this list as a guide to choosing the right filter for you and your fish.
Types of Filters
Corner (Box) Filters– Box filters are one of the least expensive options and, for the price, they work very well for small tanks (10 gallons or less). As is suggested by the name, a box filter or corner filter typically sits in one corner of the tank. While these filters are not as common as they once were, they are still a good option for hospital tanks and fry tanks because they are fairly gentle. Box filters operate using an air stone that pushes air through an air tube which in turn powers water through filter floss which filters your water mechanically. Over time, bacteria colonies build up on the filter which will biologically filter your water. Due to their obstructive visible presence in tanks, they are not recommended for hobbyists who desire a natural and aesthetically pleasing aquarium.
UGF (Under Gravel Filter) - Most UGF’s are sold in beginner aquarium kits because they are inexpensive and relatively maintenance free. They work by placing a filter “plate” under the gravel or substrate of your aquarium. An air pump then pushes water through the gravel, pulling particles in your water with it. They make an excellent biological filter, but as a mechanical filter, they do tend to clog over time. To prevent clogging, it is recommended to vacuum the floor of your aquarium regularly to remove the buildup of particles. This is a decent option for the beginning hobbyist who does not want to continually replace filtration components. It is important to remember, however, that most UGF’s do not include chemical filtration.
Sponge Filters – Though not recommended as a main tank filtration system, sponge filters are effective and commonly used in hospital tanks and small breeding tanks that contain tiny fry. Sponge filters are simple and inexpensive units that contain an airlift tube or a powerhead that forces water through a porous sponge that collects debris and bacteria. This simple set-up makes them excellent mechanical and biological filters. Consider a sponge filter if you are setting up a quarantine tank or a tank for small fry.
Power Filters– Powers filters are the most commonly used filtration system in the hobby today. They provide excellent mechanical, biological and chemical filtration. Power filters use a chamber that hangs on the back of the aquarium and an intake tube that is inserted into the tank. The tube sucks water through the chamber, passing it through a chemical filter cartridge and then through a biological sponge before the water flows back into the tank. There are many different sized power filters available at your pet supply store that can be fitted onto tanks up to seventy-five gallons, though it is widely agreed that they work best on tanks of fifty gallons or less. Many of the more advanced power filters use a “bio-wheel” instead of a sponge to better uphold the biological bacteria in your tank. Power filters are fairly inexpensive, very easy to maintain and are a great option for most hobbyists.
Wet/Dry (Trickle) Filters– More commonly used by saltwater enthusiasts, the wet-dry filter has become more popular with freshwater hobbyists. Wet-dry filters usually have a rectangular reservoir that is divided into two sections, the “wet-dry” compartment and the “sump” compartment. The wet/dry area maintains biological filtration as water trickles over a plastic plate into the wet/dry area. The water then flows through a baffle which usually contains an activated carbon unit before it is dispensed into the sump, where the water is delivered back into the aquarium. Wet/dry filters tend to range on the expensive side of filtration options but provide excellent biological filtration -- they also help tremendously in your efforts to maintain high water quality due to the fact that they increase the dissolved oxygen levels entering into your aquarium. The wet/dry filter is a great filter for hobbyists that have a large fish population in their tank.
Canister Filters – These powerful filters are great for larger tanks because they can filter large amounts of water quickly and they also offer unparalleled mechanical filtration. Canister filters also have the added benefit of being placed underneath the aquarium where it is out of sight. The canister filter uses a tube to suck water from the tank into the canister where it goes through several layers of mechanical filtration. It then goes through chemical and biological filters before the water is pushed back into the tank. Canisters require more maintenance than other filters and they are more expensive than other units. However, if you have a larger tank or are trying to achieve a completely natural look in your tank, this filtration system is probably right for you.
As you now know, there are many different options available to you when it comes to selecting an aquarium filtration system. Each type of filter has its associated pros and cons and not every filter will be the right choice for any given tank. You must not only know the parameters of your tank but also the requirements of your tank inhabitants in order to make the right choice. Due to the importance your filtration system plays in the overall performance and health of your tank, it is always good to talk with a reputable pet supply store, or more specifically your local fish dealer, about what filtration system is right for your particular aquarium. A knowledgeable salesperson should be able to answer most of your questions and will be able to help explain the maintenance requirements of the particular filter you choose.