Setting up an aquarium? It will need a filter, and that filter requires different types of aquarium filter media inside to be able to do its job. In most systems these are included, but it’s important to know which is which and what they actually do!
Below, let’s have a look at the three all-important types of filtration and what materials you can put into the filter to achieve them. That way, you can walk into the aquarium store and pick the right ones for your tank with ease.
Why does my aquarium need a filter?
An aquarium isn’t just a glass cube with water and fish inside: it’s a delicate ecosystem in miniature. Although by itself it lacks a bunch of important natural processes, like water movement and oxygenation, technology can help replace these and—paradoxically—get your tank as close to nature as possible.
One of the most important pieces of equipment in the majority of tanks is the filter. Don’t skip it, particularly if this is your first dive into fishkeeping! If you don’t know why your tank needs one or what the nitrogen cycle is, head over to the article on cycling an aquarium first. It’ll teach you all about this crucial process and the role aquarium filters play in it!
Now, let’s have a look at the different aquarium filter media you can use in your filter to help it work its magic.
Mechanical Aquarium Filter Media
Mechanical filtration is what we usually tend to associate with a filter: the removal of solid particles like leftover food, fish poop, plant bits, and other small particles that would otherwise float around in your tank. Most aquarium filters offer some degree of mechanical filtration in order to keep the water looking crystal-clear.
You can use one or more of the following to remove floating detritus and other dirt from your tank:
Filter Floss
As the name suggests, this is a flossy material that either comes in bags (think pillow stuffing) or bonded sheets that can be cut to size for use in your filter. It’s meant to do the heavy lifting in a filter, trapping most of the muck in its fine texture as soon as it comes in.
Because filter floss is usually the first stage in a filter, before even the sponge, it clogs quickly. Unlike something like sponge, it’s also pretty difficult to clean. As such, it’s usually simply replaced once it starts affecting the water flow level.
Sponges
Sponges are the superstars of mechanical filtration. Pretty much all filter types will contain some sponge (also sometimes referred to as foam), and many have multiple densities ranging from coarse to fine. This helps to remove every possible particulate size and leave the water looking crisp and clean.
Filtration sponge is found in two different types: large sheets that you can cut to size yourself, and brand-specific pads and shapes made specifically for particular filters. There’s even a type of filter that’s entirely made of sponge, suitable for lightly stocked tanks or set-ups with fragile livestock such as baby shrimp.
Unlike filter floss, sponge is pretty washable. Depending on your system, you can clean them once a week to once a month by squeezing them in clean water until no more dirt comes out. You don’t have to replace them very often either; you’ll know it’s time when the material starts to appear to break down.
Did you know? Because sponges are porous, they can house beneficial bacteria (see the section on biological filtration), though not to the degree that special biological filter material does. Still, its best to clean them using aquarium water, which affects any bacteria present less than a sudden shock with cold tap water would. Replace no more than 1/3 of the total sponge amount at a time.
Filter Sock
Often used in saltwater systems with sumped filtration, filter socks look just like their name suggests: sock-sized bags made of a felt material. Similar in function to filter floss, they act as a first defense against poop and other floating detritus.
Filter socks can and should be cleaned regularly, because they start clogging the filter flow when they get dirty (which can be pretty quick!). The best way is to turn the sock inside out, rinse off any big particles, and then toss it in the washing machine for a quick cycle without detergent.
Tip: You can customize what types and amounts of filtration media you use, but remember that water should flow through them properly in order for the media to be most effective. If the flow level is reduced, it’s time for a gentle filter cleaning. Replace filter floss or clean the filter sock, squeeze out sponges, and maybe give biological media a rinse.
Filter Rollers
Although filter socks are a classic solution, not all marine aquarists like them. It’s certainly annoying to have to clean them out regularly, and not everyone wants to put a dirty aquarium sock in their washing machine! That’s why filter rollers have gained popularity in recent years.
A filter roller does the same thing as a filter sock, but it doesn’t clog as quickly because it dispenses new, clean material as needed. Imagine those old-timey cloth towel dispensers in public bathrooms: you pull out clean towel to use, while the dirty old towel is rolled back into the machine.
The filter roller will alert you when all the clean towel is gone and it’s time to put in a new roll. Same crystal-clear water, much less time spent washing, although it has to be said that these devices do come with a significant price tag.
Biological Aquarium Filter Media
Biological filtration is all about giving a good home to the beneficial bacteria that keep our aquariums running smoothly. In an aquarium filter, biological media are placed below or behind mechanical media. First the particles are taken out, and then the water flows by the beneficial bacteria on the biological medium. This allows them do their invisible jobs of eating ammonia, nitrites, and even nitrates.
To help maintain a healthy bacterial population and keep your tank strongly cycled, the biological medium should be nice and porous.
You’ve got a bunch of different choices:
Ceramic Media
Unglazed ceramic media are a popular choice for housing our bacterial helpers. Usually coarse and shaped like short tubes (though pebble-shaped brands also exist) ceramic media tend to be placed in a mesh bag so they don’t escape all over the place.
You’ll notice how porous these materials are when you handle them. A great place for both nitrifying and denitrifying bacteria to set up shop and thrive in the long run! No need to clean your ceramic media aside from an occasional rinse in a bucket of aquarium water to remove any built-up detritus.
Bio Balls
Bio balls are made of plastic, usually around the size of a golf ball when used for larger filtration systems. Rather than being smooth, they have a textured surface with grooves, slits, and shapes. This gives beneficial bacteria places to cling on—just not all of them.
You see, bio balls tend to do great in certain filters, especially large trickle-type (pond) systems where oxygen is abundant. This is because they mostly support aerobic bacteria like the ones responsible for the nitrogen cycle.
However, more porous materials like ceramic rings or lava rock can host a greater variety of bacteria, including the rarer and more coveted nitrate-eating types. That’s why we usually recommend these over bio balls.
Crushed lava rock
Like other types of biological filter media, crushed lava rock has plenty of surface area. It’s also porous and has deep crevices, meaning it can house both nitrifying and denitrifying types of bacteria.
Lava stone’s beneficial properties are all-natural: when lava comes to the surface of the earth, dissolved gases expand and form bubbles. These are trapped when the material rapidly cools, resulting in a type of rock filled with holes.
Crushed lava rock is usually pretty cheap to buy, making it an economical option. There’s also pumice, another type of volcanic rock, but most aquarists prefer to skip this because it floats and is prone to crumbling due to its softness.
Sintered glass
It’s not that commonly used, especially compared to ceramic, but actually quite effective: sintered glass filter media are made of fused glass particles, which results in a highly porous material. Loads of surface area for bacteria to snuggle into!
Sintered glass tends to be a little more expensive than ceramic and definitely more expensive than lava rock, but some aquarists swear they get more denitrifying (nitrate-eating) action with them. Since the anaerobic bacteria involved in this process are pretty hard to cultivate effectively, this can make the price tag worth it.
Tip: You don’t have to use all of these biological aquarium filter media. It’s actually pretty hard to go wrong with this stuff, so unless you’re going for a high-tech, tightly controlled system, just use what you can find.
Chemical Aquarium Filter Media
Many aquariums get by perfectly fine on simple mechanical and biological filtration. However, sometimes you need additional chemical filtration, whether temporarily or on a permanent basis. Maybe you need to remove some medication from the water, are dealing with an emergency ammonia spike, or want to get rid of waste more effectively.
Different chemical filtration media have different properties, so it’s important to know what you should be using for your specific goal.
Here are the main compounds you’ll come across at your local aquarium store:
Activated Carbon
For a long time, pretty much everyone used to use activated carbon in their tanks all the time. It removes a wide range of unwanted stuff from the water, including dissolved organic compounds (like tannins leached from driftwood), pollutants, some toxins, and medication.
The problem with non-stop carbon use is that it also removes beneficial compounds from the water, such as the nutrients that plants or corals need to thrive. Additionally, carbon does become saturated after a while, at which point it can actually leach pollutants back in the water if you forget to remove it. It also makes medical treatments ineffective.
We keep activated carbon on hand to easily fix various aquarium-related issues, but we don’t use it on a permanent basis.
Granulated Ferric Oxide (GFO)
GFO is a handy compound mostly used to remove phosphates and silicates from the water through adsorption. After all, high phosphates can cause algae growth, while high silicates are a recipe for unsightly diatoms. Both of these aren’t just annoying, but can also interfere with plant or coral growth.
Although GFO is much more commonly used in saltwater than freshwater tanks, it works in both. Freshwater use can be handy if your tap water is naturally high in phosphates and silicates, which does happen in some areas and can lead to never-ending muck building up.
Granulated ferric oxide comes in a brownish or black small pellet or grain. You can pop some into a regular filter in a normal media bag, or use it more actively in a reactor if your tank has one. Do read the instructions and use with care to prevent the removal of too many nutrients from the water column!
Resins
Resins used in filtration media remove specific ions from the water and replace them with different, less harmful ones. They tend to be very effective at absorbing organics and heavy metals. All work on different nutrients: you can get them for ammonia, nitrates, phosphates, and more—even to soften the water.
Depending on what you’re trying to achieve, you can use specific resins as an addition to the normal filtration process. Most are regenerable, meaning you can use them over and over by recharging them using certain salts and acid or base solutions.
Zeolite
Got an ammonia problem, like in an improperly cycled tank? There are various solutions that can help get the ammonia concentration down to a safe level, including some of the aforementioned resins. Another handy solution is zeolite, which also works by means of ion exchange.
Zeolite comes in pads or little chips, which can be placed in the filter. Just be sure to remove or recharge it before it becomes saturated! Like some other chemical filtration media, it can start leaching ammonia back into the water if you don’t.
Protein skimmer
Although they often come in the form of separate units, some protein skimmers are included in filtration set-ups, so we’d like to mention them. These devices are rarely seen in freshwater tanks, but common for saltwater aquariums containing more sensitive marine life.
A protein skimmer removes organic pollutants from the water column through a process called foam fractionation. A stream of very fine air bubbles forms a foam, which carries waste along with it into a handy collection cup. Perfect for some additional waste management on top of normal filter function.
There’s a lot more to the technical side of fishkeeping than some folks think! Although the amount of different filter media available in the average aquarium store can be overwhelming, each serves its own purpose and can come in handy.
No time to learn all the ins and outs of putting together an efficient filtration system, not to mention to keep it clean? You’re not alone. That’s where FantaSEA Aquariums comes in! Our team can design, build, and maintain a healthy aquarium for you, so all you have to do is enjoy it. Contact us with your ideas!
