What is The Best Aquarium Filter Media?

In Aquarium Filtersby PaulK


Not sure what type of filter media you should use?

I put together this short guide to help you understand the best type of media to use for each stage in the filtration process. Including some you may never have heard of.

If you’re doing a DIY project or you just want to enhance your current filtration system this guide is for you.

In a typical filtration system, there are three different types of filters; mechanical for filtering out particles, chemical for filtering out chemicals and biological for absorbing the ammonia and nitrites caused by fish and other waste. There are different media or filters for each stage in the filtration process. Probably the most important is the biological filter media. It’s going to be a porous material of ceramic or sponge that can grow and store as much beneficial bacteria as possible to absorb the harmful ammonia and nitrites. Chemical filters are typically carbon filters and mechanical filter media can be filter socks or some sort of floss material.

Aquarium Filter Pad - Premium True Dual Density 12" by 72" by 3/4 to 1" Aquarium Filter Media Roll for Crystal Clear Water

Aquarium Filter Pad

Mechanical Media: These are probably the simplest of media. Mechanical filter media that come with most hang on the back systems are going to be filter pads. These are effective for smaller tanks with less fish because they are simply a pad with not much to it. Some of the better media to use are filter socks designed for smaller particulates or poly-fil material that you can buy on Amazon. If you want to get serious have a coarse mechanical filter first and finer filter sock second for maximum filtration. Keep in mind that you have to clean out the filter(s) at least once per month so particles don’t build up and clog the filter.

Chemical Media: The most common type of chemical filter is carbon. Carbon is effective at removing odors, medication and other chemicals harmful to fish. These filters should be changed out every month as well. Other chemical media types include Poly filter, granular ferric oxide, crushed coral, peat, peat granules and ammonia chips. You can also buy something like Seachem Purigen, a chemical resin that polishes the water crystal clear. In most cases, a Carbon filter is all you will need.

Biohome Mini Ultra Filter Media (1 LBS)

Biohome Media

Biological Media: This is the one media you do not replace because you need to keep the beneficial bacteria that are built up over time. It’s probably the most important filter media, so you need a good one and the more the merrier. Biological media is there to provide surface area for bacteria to grow. A good porous material like ceramic has lots of channels and pores that provide massive amounts of surface area.

Most hang on the back filters will have a sponge type filter or a bio wheel that fit in the housing unit or return spout. These will work pretty well for smaller tanks, but for larger tanks, you’ll want to upgrade the media. For canister filters and sumps, people will use ceramic or lava rocks. For a moving bed filter, you need a moving bed media like K1 or helix which is plastic media that grow stronger bacteria. Airstones at the bottom of the chamber provide nice aeration so bacteria will grow and the tumbling action keeps the media clean.

What Filter Media Should You Use?

The water flow should go through one or two mechanical filters first. If you use two mechanical filters, the first one should be coarse like a filter pad or polyfill. The second one should be for finer particles like a filter sock. Keep in mind that the finer the filter, the more you will have to clean it but the water will be pretty clear. Next, the water should flow through the chemical filter which is usually carbon. Then the water should flow through the biological filtration of either ceramic rings in a media bag or thick sponge.

Best Mechanical Filtration

Filter socks would be the best solution for clear water, but require frequent maintenance and aren’t designed for many types of filters.

Pillow casing or floss, does a very good job. You have to be careful though not to get any that are bleached or dyed as that can be harmful to your fish.

Open cell polyether filter foam. The advantage is this can also double as a biological filter.

Quilt batting that is 100% polyester. Make sure there are no additives like fire retardants in the material.

Polyester fiberfill, also called filter floss does a fabulous job.

Polyester mesh fabric can be purchased at your local fabric store. There are many different grades and colors available.

Woven plastic filters are not the most effective, but can be used in conjunction with other filters.

Coarse sponges are lower maintenance but don’t do as good a job in clearing the water.

Can You Reuse Filter Media?

Sponge filters for biological filtration can be lightly washed and need to be reused. You don’t want to replace it or you’ll have to start over growing bacteria. Mechanical and chemical filters can get pretty bad after a few months of cleaning them before you have to replace them. If you use sock filters, you can wash them by either throwing them in the washer with a capful of bleach (not soap or detergent) or throw them in a bucket with a capful of bleach. Another way to wash them is to use a power washer and simply wash off the debris.

Can You Use Old Filter Media?

If you’re starting a new tank and want to get a head start on cycling the tank, it’s a good idea to use the old biological media in the new tank. Since the beneficial bacteria is already there ammonia and nitrites from the fish will be absorbed quickly.

Which Filter Media Is Best?

For biological filtration, anything that gives you 0 ammonia and 0 nitrite readings is the best media to use. Porous ceramic material or lava rock work the best in canister filters. I highly recommend Biohome or Biohome Plus for ceramic media. It’s a very porous material that grows both types of bacteria for ammonia and nitrite absorption. Use a media bag to hold them in. Thick sponge filters work well too.

For mechanical filtration, one coarse filter and one fine filter work best. Make sure the water flow through here first so the biological media doesn’t get full of muck. Use a floss material like non-treated pillow casing and/or a filter sock. Filter socks come in various microns from coarse to fine. The finer the media, the more you will have to clean it.

What Filter Media For Sump?

With a sump filter system, you have more options as to what to use for media. You are not bound by what comes with the box so you really have some flexibility. Really you would use the same type of media mentioned above just more of it. You can experiment with different types of media for mechanical and biological filtration. You also have plenty of room for two mechanical filters, one coarse and one fine.

How Much Filter Media Do I Need?

As long as you use a good biological media like porous ceramic or lava rock you shouldn’t need more than one media bagful. Sometimes on larger tanks over 75 gallons, I use 2-3 bags of porous ceramic media. If you have a power hang-on-the-back filter with a sponge, use as thick of sponge that will fit in the chamber. Usually, there is extra room in the chamber for an upgrade to your stock filter.

How To Clean Filter Media

A very important aspect of fishkeeping is knowing how to clean your filter. Now, when I say the word “clean” I don’t really mean “clean”. It’s ironically the worst word to use when we are maintaining our filter.

To clean your filter don’t clean your filter.

That’s probably one of the most illogical sentences I’ve ever said. stay away from soaps, detergents and tap water when you’re cleaning the bio media that’s in your filter. All these products and the chlorine in your water will kill the bacteria living in your filter. This bacteria is what keeps your fish alive without bacteria you can get ammonia and nitrite spikes and these are extraordinarily harmful to your fish. You can lose your whole tank because of this.

If you notice after you clean your filter that the water becomes cloudy, that’s because there’s a bacterial boom and that is one of the signs showing us that there’s ammonia and probably nitrite in your aquarium. most soaps and cleaning products will leave residue in your aquarium making it inhospitable for your fish. your bio media and sponges should be replaced every six months to two years when they start to break down. Until then wash your bio media every one to two months wring out your sponges in a bucket of aquarium water make sure to get all the gunk out.

Our objective is to remove the waste and keep the bacteria intact.

Every six months, make sure to remove the waste buildup in your bio media by washing it in a bucket of aquarium water this will remove the waste and protect the beneficial bacteria. Never wash the sponges and the bio media at the same time because you might kill too much beneficial bacteria in the process Filter pads are great, they trap micro particles and keep your water clear if ever you’re you look at your water and you see they’re always these little particles inside it, use one of these. These should be changed every one to two months. if you leave it too long in your filter and you don’t change it after one to two months, it’ll get filled with organic matter it’ll just be filled with waste and it will pollute your water. Also, it’ll change the water pressure coming out of your filter making it less efficient and oxygenating your water a lot less. if you have to change it every two weeks you’re probably feeding too much and the food gets trapped in your filter. this is picking it up. so if ever you find you’re changing your poly filter very often feed less and should be fine.

When taking care of your filter make sure that you change the carbon. The carbon should be changed every one to three months depending on the brand that you use. Each product has a different lifespan so put an alarm on your phone and a little note on your filter notifying you when to change it. If you don’t respect the lifespan of your product the elements that are absorbed will be spewed back into your aquarium this happens with most activated carbons on the market. This is also the case for your tap water filter if it’s been over six months because that’s a usual lifespan for those, maybe it’s time you changed it. My best advice if you have cartridge filters is getting another filter. I’m not saying you should throw your cartridge filter out, I’m saying you’re gonna need a second filter, especially if you really want to fill this tank up. the great advantage of cartridge filters is their ease of use. You have cartridges with a poly filter and carbon that you change every month and you alternate them.

There’s also another insert that helps colonize your beneficial bacteria. their huge disadvantage is the lack of surface where the beneficial bacteria can colonize. there’s not a lot. if you want to really stock your aquarium you’re gonna need more beneficial bacteria so if you have a canister filter and a cartridge filter, this is great because you don’t have to open your canister filter every month to change the carbon you just do it on the cartridge filter which is on the outside and a lot easier of access. For Sponge filters, once a month wring them in a bucket of their aquarium water. this will take out the gunk and protect the beneficial bacteria this is what I do for all my growing tanks.

Regular maintenance and sufficient filtration should keep your water crystal clear. Don’t over clean your aquarium.

How Long Does Filter Media Last?

Bio media should never be replaced, so would last you as long as you have the tank.

Poly filters for mechanical filtration should be cleaned every other week depending on how fine the filter is, how much waste is in your tank, and how many gph your filter cycles the tank water. When the filter starts to turn dark brown or black, they should be replaced. Usually after 2-3 months.

Carbon filters should be changed every three weeks or so. Honestly, most fishkeepers don’t even use carbon filters unless they are trying to filter out medication. You could save your money and not even use one.

What is KDF Filter Media?

Kinetic Degradation Fluxion (KDF) is a high-purity copper-zinc formulation that uses a basic chemical process known as redox (oxidation/reduction) to remove chlorine, lead, mercury, iron, and hydrogen sulfide from water supplies. The process also has a mild antibacterial, algaecide, and fungicide effect and may reduce the accumulation of limescale.

KDF process media is used in pre-treatment and primary treatment applications to supplement or replace existing technologies in order to extend system life and to reduce heavy metal, chlorine and hydrogen sulfide contamination. It is often combined with other technologies to achieve superior overall results. Because of its effectiveness at higher water temperatures, it is often used on shower water filtration systems to remove chlorine and other contaminants.

The technology was developed by KDF Fluid Treatment, Inc. in the mid-1980s and was patented in 1987. KDF filter media meets EPA and Food and Drug Administration standards for levels of zinc and copper in potable water and is certified by NSF International to its Standard 61 for drinking water.

What Is Birm Filter Media?

Birm® is an efficient and economical media for the reduction of dissolved iron and manganese compounds from raw water supplies. It may be used in either gravity fed or pressurized water treatment systems. Birm® acts as an insoluble catalyst to enhance the reaction between dissolved oxygen (D.O.) and the iron compounds.

In groundwaters, the dissolved iron is usually in the ferrous bicarbonate state due to the excess of free carbon dioxide and is not filterable. Birm®, acting as a catalyst between the oxygen and the soluble iron compounds, enhances the oxidation reaction of Fe++ to Fe+++ and produces ferric hydroxide which precipitates and may be easily filtered. The physical characteristics of Birm® provide an excellent filter media which is easily cleaned by backwashing to remove the precipitant. Birm® is not consumed in the iron removal operation and therefore offers a tremendous economic advantage over many other iron removal methods.


Getting the filter media right goes a long way to having a clear, non-toxic fish tank. Hopefully, this article steered you in the right direction and increased your understanding a little without having to fish (pun intended) around the web.

What is your biggest concern or frustration with fishkeeping? Let me know in the comments below.

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Power vs Canister Filters: Which One is Best?

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