Fish Tank Filters: Which One Should You Get?

What is the first thing people think of when they hear that you keep fish as pets? Most people think back to their great aunt’s goldfish tank that was covered in mystery slime and smelled of stagnant water. But you and I know the secret to having a beautiful aquarium with crystal clear water… clearly, we just need to find the perfect fish tank filter!

Why do Aquariums Need Filtration?

As one of the key components of an aquarium, filtration is responsible for moving and cleaning the tank water, making it safe for fish to live in. There are three types of filtration: chemical, biological, or mechanical. There are some filters that work better than others, so let’s take a look at each type.

Mechanical filtering uses sponges and filter socks. Filter floss pads are used to physically strain out any debris in the water. This is similar to 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. After the media has been saturated with impurities, chemical filtration is no longer able absorb any pollutants from the water.

Examples of mechanical, biological, and chemical filter media

Bottom Line: mechanical filtration makes your water clearer, biological filtration makes your water safer, and chemical filtration is something best saved for removing impurities from the water.

What Are the Most Popular Types of Filters?

Now that you’re familiar with what filtration does for an aquarium, let’s talk about the actual equipment you can purchase (in rough order of most to least common).

Sponge filter

Aquarium Co-Op sponge filters

This most basic of all filters requires at least three components: a sponge filter (which sits inside the tank), air pump (which sits outside the tank), and airline tubing to connect them. The air pump pushes air through the tubing into the hollow cavity inside the sponge filter. The sponge walls pull water through the tubing, allowing the bubbles to draw in water.

Advantages: There are many pros to this device. It is easy to use, cheap, and durable. It provides good water circulation and surface agitation, while being gentle enough to avoid sucking up fish fry, shrimp, and other slow-moving creatures. To prepare for an emergency, you can buy battery-operated pumps that will pump air to the sponge during power outages.

Cons: The sponge filter takes up physical space in the fish tank, so you may want to hide it behind a rock, plants, or other aquarium decor. There is no way to add chemical filtering if you need it. The bubbling sound that a sponge filter makes is not something I like, but it can be fixed by using a little bit of air stone.

Summary: Spongefilters are often found in fish shops, fish room, and breeding areas because they are so reliable and affordable. Use what’s proven to work.

Hang On-Back Filter

Hanging-on-back filter to nano tanks

Just as the name describes, a hang-on-back filter sits on the top rim of an aquarium with the filter box hanging outside the tank and the intake tube lowered into the tank. Water is sucked up the intake tube via the filter’s motor, passed through all the media in the filter box, and then typically returned back into the aquarium like a mini waterfall.

The pros: I love the flexibility of the filter media and the ability to include all three types. In fact, I’d say a hang-on-back filter is even better at mechanical filtration than a sponge filter because you can add a fine filter pad to really polish the water. The device is very simple to service since most of the media is outside of the aquarium, allowing you to easily remove the media for gentle washing. The AquaClear filter that I have has a variable flow rate. This allows me to adjust the water circulation according to my needs.

Cons: Because a power motor drives the water flow, there’s a chance it can burn out if the filter runs dry or accidentally sucks up sand (use a pre filter sponge to prevent the latter). Additionally, if you don’t like the waterfall sound, just raise the water level in your aquarium and you’ll barely notice the noise.

Summary: This filter was my first and still is in use today. As a popular staple in the freshwater aquarium hobby, the hang-on-back filter excels in all three arenas of filtration and has extremely flexible options for hot-rodding it to your tastes.

Canister filter

A canister filter is essentially filtration in a plastic cylinder or box form factor that often sits under the tank, with intake and output hoses that reach into the aquarium. A motor pulls water into the canister. The water then travels through several filter media trays and is returned to fish tank.

Pros: Just like the hang-on-back filter, the canister filter takes up very little room inside the aquarium and is highly customizable. Some models include extra features such as an inline heating, UV sterilizer, or automatic priming. This filter is considered to be one the most powerful and quiet on the market.

Cons Also, that nifty little canister is pretty difficult to service, requiring you to practically disassemble the whole setup every time you want to clean out the insides. Note: There is a greater risk of flooding during maintenance. Keep those towels handy! Finally, because the filter media lives outside the aquarium in a closed box, there’s a greater risk of suffocating and killing off your beneficial bacteria during a power outage.

Summary: If your discus needs extremely clean water or you have an African cichlid aquarium with high bioloads, then this might be the right product for you. This premium product is worth the extra time and money.

Fluidized Bed Filter

Ziss moving filter, powered with an air pump

Fluidized bed filters were traditionally used for DIY filtration. But, now, there is a smaller, ready-to-use version called the Ziss Bubble Moving Media filter. The media swirls around like fluid when water flows through a chamber made of small media granules, such as sand or pellets. Because the media is constantly in contact with oxygenated waters, this constant churning greatly boosts bacteria growth.

Pros: The Ziss filter is air-driven like the sponge filter, so it has very few mechanical parts to break and provides plenty of surface agitation for increased gas exchange. It has a sponge prefilter on the bottom to prevent fry from being sucked up. This is also easy to remove for maintenance. As a device focused on biological filtration, it’s great for goldfish and turtle aquariums with high bioloads – and unlike sponge filters, the hard plastic is too hard for turtles to chomp through!

Cons: This filter is relatively tall at 11 inches, so it’s only suitable for taller tanks (not a 10 gallon or 20 gallon long aquarium). Like the sponge filter, it’s not as customizable for adding chemical filtration or more mechanical filtration. The noise level is comparable to that of a sponge filter, mainly due to the bubbles and pump.

Summary: To improve biological filtration, a fluidized-bed filter may be a good option. A single Ziss Bubble Bio filter can handle 20-40 gallons of water. It can also be used in conjunction with other filters.

Live Aquarium Plants

Bottom Line: Start with easy beginner plants like java fern and anubias that don’t require any special lighting or substrate. Your aquarium will look amazing and your fish will thank you for it!

Which filter should I choose?

Ah, the golden question that every aquarist wants to know. First off, there are plenty of other filters that I didn’t cover (e.g., internal filters, sumps, and undergravel filters). There is no one “best” filter. Instead, there are many tools that can be used to accomplish different tasks. Consider the needs of your aquarium – such as your stocking levels, water circulation, ease of use, and budget – and pick the solution that works for you. Have fun filter shopping!