We independently research, test, review, and recommend the best products—learn more about our process. If you buy something through our links, we may earn a commission.
Keeping the water clean is one of the most important steps when taking care of aquarium. Investing in a quality filter can ensure your water stays fresh and clean without too much effort. To choose the best one, it's best to know the different types of filters out there.
"There's three main types of filtration in any aquarium system. And that is biological filtration, chemical filtration and mechanical filtration," says Nic Tiemens, co-founder of Infinity Aquarium Design. "Biological is the ability to break down harmful organics like ammonia, like nitrate, like nitrite, so you want to make sure you have a filter that has a good reputation of breaking down harmful organics." Mechanical filtration is simply the removal of particulates in the water. Finally, chemical filtration is the addition of chemical media like carbon or phosphate remover, things that will really clear your water so you get clarity and purity.
For crystal clear water, check out the best filtration systems below.
Best Overall: MarineLand BIO-Wheel Power Filter
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.
The Marineland Penguin Power Filter filtration system works 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.
Best for Freshwater: Penn Plax Cascade 700 Canister Filters
Freshwater tanks aren’t quite as challenging to maintain as saltwater setups, but you’ll still want to buy a reliable filter to keep your water clean and contaminant-free. Canister filters like this one from Penn Plax provide strong mechanical, chemical, and biological filtration, and they sit outside your tank—making them easy to conceal. Its 265 GPH flow rate can be used in tanks holding up to 100 gallons, and a simple push-button primer makes setup virtually foolproof. The result is clear, fresh water that’s free of waste, excess food, ammonia, and other toxins.
The Penn Plax Cascade filter is unbeatable in value and performance, operating quietly but offering a high degree of customization thanks to its three media baskets and rotating flow valves. While it can also be used with saltwater tanks, it’s an especially solid buy for anyone maintaining a freshwater aquarium.
Best for Saltwater: AQUATICLIFE RO Buddie Reverse Osmosis Systems
Saltwater fish and marine life have different needs than their freshwater cousins, and improper water conditions can quickly result in a dangerous and unlivable environment. That’s why you’ll want a filter that includes features like deionization and reverse osmosis, which forces water through a membrane to remove impurities. The Aquatic Life RO Buddie combines affordability with the high-powered filtration you’ll want in a saltwater tank, with three models offering either three-stage reverse osmosis or four-stage reverse osmosis deionization (or RODI) in a single small-footprint unit.
Customers say the Aquatic Life RO Buddie has resulted in a tank full of happy, healthy saltwater fish and coral. The reverse osmosis feature is especially useful if you’re using tap water with a high level of hardness (or dissolved calcium and magnesium), which can be a survival risk for saltwater fish. Using the filter’s reverse osmosis and deionization system, some customers have brought hardness down to zero even when using water from the kitchen tap.
Best for 20-Gallon: Tetra Whisper IQ Power Filter for Aquariums
Even if your tank is on the smaller side, you’ll still want to invest in a great filter. The Whisper IQ Power Filter is just right for 20-gallon aquariums, with an adjustable intake that telescopes up and down depending on your tank’s needs. Its StayClean filtration system is easy to maintain and keeps fish healthy, removing toxic ammonia and nitrites while promoting the growth of healthy bacteria. It’s also extra-quiet thanks to a soft barrier separating the motor from the filter.
The Whisper IQ Power Filter starts up immediately with no priming required, and it’s one of the best small, cartridge-based filters on the market.
Best for 75-Gallon: Seachem Tidal 75 Large Aquarium Fish Tank Filter
For large, 75-gallon tanks, our pick is the Seachem Tidal Filter. It has a flow rate of 350 GPH, and a self-priming pump and self-cleaning impeller for easy maintenance. An alert feature also lets you know when your filtration setup needs to be adjusted or otherwise inspected. The filter includes an extra-deep basket to accommodate the media of your choice (it includes Matrix, a highly porous biomedia), and a powerful skimmer to keep your tank’s waterline clear.
It has a three-point intake, and it produces strong, consistent circulation within 75-gallon tanks. The media basket is also easily accessible for cleaning. The Seachem Tidal Filter hangs on the back of your tank but offers a higher degree of customization than most filtration systems with a “HOB” design.
Best Wet-Dry Filter: Eshopps Inc. WD-75CS Wet Dry 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, 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). However, setup can be challenging for novices—not unusual for wet-dry filtration systems.
Best Undergravel: Lee's 40/55 Premium Undergravel Filter
True to their name, undergravel filters are placed beneath your tank’s substrate rather than outside or on top of your tank. Lee's 40/55 Premium Undergravel Filter helps promote the growth of beneficial bacteria in your tank’s gravel, breaking down waste materials through a natural biological process. It can also be paired with a conventional power filter for even clearer water. It includes carbon filtration cartridges, and its plates are designed using a specialized plastic that resists splitting or cracking—an important quality considering it’ll be fully submerged in your tank.
The Lee’s 40/55 Premium Undergravel Filter works well with the style of most tanks, as the all-black design makes it blend in with gravel for a natural, unobtrusive look. It also does a great job of keeping tanks clean, with especially stellar water quality when it’s used in tandem with a second power filter.
Why Trust The Spruce Pets?
For additional background on aquarium filtration systems, we spoke to Nic Tiemens, co-founder of Infinity Aquarium Design, who spoke about the different types of filtration systems.