Whether you’ve had aquariums before, or you’re brand new to the hobby of fish keeping, it’s always great to get suggestions for filters. Seeing as they are a necessity if you want clean, fresh, and easily maintained water for your fish, there are plenty of different types, each different enough to fit your specific needs.
Fish aren’t the cleanest pet to own. Unlike cats or dogs whose waste you can easily pick and throw away, fish need a filter that will separate their clean water and dirty water. It also serves as a breeding ground for bacteria that is healthy for your fish and allows for water movement that will keep fresh oxygen available.
Generally speaking, to effectively maintain an aquarium a filter should run all the water in the tank through the filter at least four times each hour. When choosing a filter it’s best to know what kind of filtration it offers, whether that be biological, chemical, or mechanical, or a combination.
Buying the right filter for your specific needs can get confusing though. It all depends on what type of fish you own, how big your aquarium set up, what kind of water you’re housing, and the pH balance needed to keep your fish healthy. So keep reading to see the differences between the eight most popular types of filters and my top recommendations for each one.
1. Box Filters
Box filters are often also referred to as corner filters or internal filters and are historically the first filters made available for home aquariums. These filters are very affordable and can be filled with a large variety of filter media (i.e. zeolite.)
Box filters are usually compact units that can attach to the glass that is inside of an aquarium, and are best for smaller aquariums, usually 20 gallons or less.
Do keep in mind that because they are meant for smaller tanks, they have a less powerful intake flow. This isn’t great for larger fish, but perfect for smaller fish, and even fry who can easily get sucked into a filter. Some of them need air pumps and an airline move water through it that create bubbles that are seen in some tanks.
They usually range from around $8 to $30.
My pick for the best box filter (for a smaller tank) would be the Tetra Aquarium Filter (AQ-78056), Up to 4-Gallons.
2. Canister Filters
Canisters are a great filter for tanks that are larger than about 40 gallons. They are positioned outside of the tank and can easily be hidden from plain sight, meaning you can keep your tank looking clean and unobstructed in the interior.
Canisters are also fantastic in that they utilize mechanical, chemical, and biological filtration. They use pressurized force that pushes water through the filter media rather, than around it, meaning heavy amounts of waste can easily be taken care of. Adding a biowheel can also aid in biofiltration.
The only downside is that these filters can be difficult to disassemble and reassemble when you need to clean them out. Other than that, they are absolutely perfect for saltwater aquariums or fish the require a lot of living plants.
They usually range from around $90 to $500.
My suggestion for a Canister filter is the OASE Indoor Aquatics Biomaster Thermo 350, which also has a built-in heater.
3. Diatomic Filters
Diatomic filters are a specialty filter that removes small particles, leaving your water looking extremely crisp and polished. They operate by pumping water through a layer of exceptionally small particles in order to clean it.
They are really only used when diatomic algae become a problem but also come built into regular filters so you can switch them in for short periods of time
They usually range from around $40 to $100.
My suggestion for a Diatomic filter is the Marineland® Polishing Internal Filter, which is perfect for tanks up to 100 gallons.
4. Fluidized Bed Filters
Fluidized Bed Filters are a newer type of filter and are fantastic at cleaning using sand or silica chips as a medium. The units hang from the back of the tank, where water can easily run down through the sand acting as a natural filter.
They are also sometimes referred to as a suspended particulate filters.
Something great about these types of filters is that nitrifying bacteria colonies grow on the particles of sand and will naturally process ammonia and Nitrate as soon as the water passes through. The water pumped into the bottom will cause the sand or pellets to constantly be pushed up by the current and fall down, so it’s natural that this filter will sort of resembling a snow globe.
Water does need to be pumped into it, so it’s best to get one if you don’t get a kit that includes one.
The average cost for a fluidized bed filter ranges anywhere from $50.00 to $150.00.
My suggestion for an affordable Fluidized Bed Filter is the Lifegard Fluidized Bed Filter.
5. Power Filters
Power Filters will sometimes be referred to as hang-on-back filters, and they are the most common type of filter used in aquariums. This is largely due to the fact that they are fantastic at performing mechanical, chemical, and biological filtration at the same time.
The mechanical filtration is done through a filter pad or floss, the chemical filtration is done by the use of water flowing through a carbon filter, and the biological filter is achieved by bacteria that naturally form inside the cartridge.
This filter will hang off the back of your tank, as its alternate name implies, and will suck up water through a siphon tube. Extremely easy to install and even easier to maintain, they are an easy pick for any newbie to the world of aquariums.
The average cost for a fluidized bed filter ranges anywhere from $10 to $150.
My suggestion for a power filter that will work for a twenty to a fifty-gallon tank is the AquaClear, Fish Tank Filter, 20 to 50 Gallons, 50v, A610.
6. Sponge Filters
Sponge filters are fantastic options for tanks that have or will have fry, as the sponge will keep them safe from being sucked through a powerful pump. They are also great for a hospital isolation tank as it can provide nitrifying bacteria.
It easily can fit over a tube from a powerhead or air pump, and as water is pumped through the bacteria will naturally grow, providing both bio and mechanical filtration.
It’s important to note that the sponge needs to be cleaned with tank water, as tap water could easily kill the bacteria growing on the sponge that is ultimately beneficial.
Sponge filters can range in price anywhere from $5 to $40.
A great option for a sponge filter is the AQUANEAT Sponge Filter, for Aquarium Fish Tank, Betta, Nano, Shrimp, Fry, Biochemical Filter.
7. Trickle Filters
These types of filters are also called wet/dry filters, as they are designed to be exposed to as much air as possible. The aquarium water will trick over media like floss, strands or plastic balls, and the exposure to air will foster beneficial bacteria that will naturally break down waste. You can also provide chemical filtrations imply by putting that type of media in the filter.
Trickle Filters are very popular with saltwater tanks, but are also growing within the freshwater community. They aren’t perfect, though, as they will clog easily if you don’t use a mechanical pre-filter.
Trickle filters can range from affordable to costly, with prices anywhere from $30 to $300.
A great option for a Trickle Filter is the AE-SHOP KZKR Aquarium Filter Fish Tank.
8. UGF (Under Gravel Filter)
The Under Gravel Filter is great for when you want to place your filter out of sight. Using a plate filter that is put under the substrate, and also an air pump that pulls water down through the substrate, it will easily take the particulate matter with it.
While easy to maintain and set up, and fairly inexpensive, there are a few downsides. They don’t really feature an advanced biological filtration, there isn’t any chemical filtration, and they can’t be used in aquariums with live plants.
Costs of Under Gravel Filters range from $8 to $60.
A great option for a UGF is Lee’s 50/65 Premium Undergravel Filter, 18-Inch by 36-Inch.
Different Types of Filtration
To better understand what your filter will be cleaning, you need to understand the difference between Biological, chemical and mechanical waste.
Biological Filtration – For the best biological filtration, you will need rocks or sand at the bottom of your tank that bacteria can attach to, along with oxygen-rich water. This way, beneficial bacteria can break down nitrite and ammonia, which it turns them into a compound nitrate, which is much less toxic to your fish.
Chemical Filtration – This is the process wherein chemical additives remove waste that has been dissolved in the water. The most common type of chemical filtration uses activated charcoal.
Mechanical Filtration – Mechanical filtration is the machinery that dirty water in and clean water out before free-floating waste turns into something more dangerous. It does not work alone, though, and needs to be combined with some other form of filtration due to the fact that it doesn’t remove or convert ammonia or nitrate.
It’s best to clean or replace your filter every two to four weeks so that it doesn’t get clogged up with waste, and harmful chemicals don’t muddy up your fish’s clean, aerated water.
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