Fish are fantastic pets, but they’re not the cleanest animals on the planet. Whenever fish do their business, everything is left floating around in the tank for all to see. If you want to keep an aquarium clean and make sure the water is healthy for your fish, you’re going to need a filter. The best aquarium filters will make sure your water quality stays consistently well while your tank water looks crystal clear.
This way, you’ll get to enjoy watching your little critters move around while also helping make sure their habitat is as friendly and livable as possible.
Picking the right filter for your new aquarium can at first seem like an overwhelming task. So may different types and sizes of filtration are available, one needs to sift though all the choices to find the correct match. In today’s article I’ll highlight my favorite filters for a few different ranges of aquarium sizes.
Why Is An Aquarium Filters Important?
The aquarium nitrogen cycle is the natural process that breaks down toxic waste products in the water and transforms them into safe compounds.
Without this process, keeping fish in an aquarium would be impossible, so let me explain for anyone who’s not familiar with it. Fish constantly put off waste, both urine and feces. Gross, but true.
All that waste sinks to the bottom of the tank and starts to decompose. As it breaks down, it puts off ammonia (NH3). This is bad news because ammonia is highly toxic.
Left on its own, the tank would quickly become unlivable. The fish would keep putting off waste which would make more and more ammonia until the water became completely toxic and all the fish died. This is where the nitrogen cycle comes in. In an established tank, there are millions of beneficial bacteria living in the filter.
5 Best Aquarium Filters of 2021:
I’m really impressed with this Tidal filter made by Seachem. This filter has a ton of room for media. The large filter housing comes with its own reusable mechanical filter media. The rest of the space can be filled with whatever chemical and/or biomedia you want.
This filter features an internal motor that hangs inside the main aquarium. There are many benefits to this design. Filters with internal motors don’t need to be primed (filling up the back of the filter with water) so they’re really easy to get running.
No worries that the filter won’t start up on its own after a power failure or a water change. It will immediately start to suction water as soon as it has power.
Internal motors are also very quiet because the water absorbs any sound the motor makes. As much as I like this filter, there are some downsides. The biggest for me is that you can’t make this filter safe for tiny inhabitants, like ornamental shrimp or fish fry.
Since there’s no lift tube, there isn’t a way to attach a sponge pre-filter to keep little guys from getting sucked into the filter, where they can be injured and/or killed.
- Quiet operation
- No priming
- Large biomedia capacity
- Not safe for shrimp or fry
- Surface skimmer can suck up food
A great filter doesn’t need to break the bank. For just over $25, Marineland’s Penguin Power Filter hits all the marks—and then some. It’s three-stage filtration process first removes dirt and debris, then filters out chemical impurities and biological toxins (like the dreaded ammonia).
It requires little setup, making it a natural first purchase for beginner aquarists, and has a certified flow rate of 350GPH, which is appropriate for tanks up to 70 gallons in size. Cartridges are also included, with the correct type paired with your filter’s model—it’s available in four based on the size of your tank.
Online reviewers write that the Marineland Penguin Power Filter is a superb filtration system for nearly any tank, with most mentioning that it operates quietly and effectively. Its unique BIO-Wheel gets called out for additional praise—it removes ammonia and nitrites on contact while helping grow beneficial bacteria that aids in natural filtration.
- Easy access to media
- Innovative design
- Large biomedia capacity
- Easy to make shrimp/fry safe
- Needs to be primed
- Can be a pain to get started
Sponge filters were once the simplest type, used mostly for hospital and breeding tanks and raising fry. They are a very gentle filtration system powered by an air pump that sucks your dirty water through a fine sponge-covered intake. Their primary job is to remove large visible debris and waste from your aquarium water.
Modern sponge filters can also include a biological stage, which may only be helpful if you’re using it in a tank longer-term rather than for a sick fish. Their ability to filter out debris is limited and they require weekly cleaning to prevent them from being clogged. It takes a month of use to cycle your water and establish healthy bacteria.
I keep sponge filters on hand for emergencies, but they don’t offer enough filtration for my planted tanks or large community set-ups. Since they can’t chemically neutralize ammonia I don’t rely on them as my primary form of filtration. But they are a very good option for small Betta or freshwater shrimp aquariums!
- Simplest type to set-up, use and maintain
- Powered by an air pump with a natural low-flow rate
- Limited filtration ability, so you’ll still have to do weekly water changes
This is a hanging external power filter from AquaClear. It’s available in 5 different versions to accommodate tanks of different sizes. You can purchase it for 5 – 20, 10 – 30, 20 – 50, 40 – 70, or 60 – 110 gallon tanks. These different sizes are capable of pumping 100, 150, 200, 300, or 500 gallons per hour respectively.
As a larger power filter, your tank will get mechanical, biological, and chemical filtration from this filter option. There is space inside for three cartridges, one for each type of filtration media. The space allocated to cartridges provides a large surface area for each, making for better biological filtration throughout.
Each cartridge can be individually replaced, so you can choose what to put in each slot and you can change them one at a time to avoid losing beneficial bacteria in the process of cleaning.
When you purchase the filter, it comes with an AquaClear foam insert for mechanical filtration, an AquaClear activated carbon filter cartridge for chemical filtration, and an AquaClear Biomix filter with ceramic rings for biological filtration.
The intake brings water through the U-shaped tube and into the bottom of the filter, where the water then rises through the filter media and pours back into the tank.
- Fits well on most tanks
- Very little noise, even for the larger sizes
- Cartridges can be exchanged for any type of filter media you prefer
- Easy to clear when necessary
- Small grain sand substrate can clog or disrupt the filter
A wet-dry filter uses biological media that’s exposed to both your tank’s water and the air outside of it. Because it results in a high level of beneficial bacterial growth while efficiently processing waste materials, it’s especially well-suited to saltwater tanks. The Eshopps Wet-Dry Filter is an expensive buy at $285, but it’s a one-stop shop containing nearly everything you need to build your wet-dry rig.
The set includes an overflow box, bio balls, filter pad, and return nozzle, along with a specialized wet-dry drip tray filter to process ammonia and nitrites.
Customers write that the Eshopps is a top-quality wet-dry filter, with a high degree of craftsmanship even as it includes most of the essential components in one convenient package (you’ll still need a pump).
While setup can be challenging for novices—not unusual for wet-dry filtration systems—it’s an overall great product, and can be used in tanks from 10 to 75 gallons in volume.
- Unique priming handle
- Huge biomedia capacity
- Central handle for media removal
- Canister filters require more involved maintenance
What to Look for in the Aquarium Filters
There’s no outright best fish tank filter for all tanks, so you need to understand a few things about what differentiates one filter from another to make an appropriate choice for your own tank. Here are the main things you need to know:
- Size Matters: It’s worth emphasizing again that aquarium filters need to be matched to aquarium size. You can’t tell water quality by looking at the water itself, but it could be affecting the health of your fish, live plants, and other marine life.
- Amount & Types of Fishes: Beyond your aquarium’s size, the number of fish and plants you have will also make a difference in your filter choice. The best fish tank filters will be able to keep up with your fish stock without the water quality reducing too quickly. The more fish you have, the stronger your filter needs to be to keep up with all of their waste.
- Flow rate: Filters are rated by their capacity and power (to determine how many gallons they can handle), but their flow rate is also an important consideration. The flow rate refers to the speed at which the tank water passes through the filter.
- Aquarium Filter Brands: Just like with any other products, there are certain brands that produce filters known to be more reliable than others. Some of the most well-known brands for filters include Tetra, Pluval, Marineland, EHEIM, Penn Plax, and AquaClear.
Why do Aquariums Filters Need Filtration?
The three main types of filtration are mechanical, biological, and chemical filtration. Certain filters are better at one type versus another, so here’s a brief overview of each category:
- Mechanical filtration uses sponges, filter socks, and filter floss pads that physically strain out debris from the water, much like a coffee filter. Mechanical filtration acts as a garbage can that collects trash – which means you as the fish owner are still responsible for cleaning the filter media (in other words, “emptying” the trash can before it overflows).
- Biological filtration uses beneficial bacteria or aquarium plants that can consume the toxic ammonia and nitrogen compounds that result from your fish’s waste. Beneficial bacteria grows on any surface, including the walls and gravel in your aquarium, so many filters come with biomedia or bio-rings with high surface area to provide more places for the bacteria to live.
- Chemical filtration uses activated carbon or special resins that can remove medications, tannins, and other impurities from the water. Once the chemical filtration becomes saturated with impurities, the media is no longer able to absorb pollutants from the water.
These options will give an idea as to what we think are some of the best aquarium filters on the market. Most of these filters come in different sizes and selecting one that is in the correct range for your aquarium will be crucial to maximize the ability of the filter to properly clean your water.