Canister Filter Media Order: 4 Layouts for Planted Tanks

Coarse mechanical media first, then progressively finer foam, then bio-media last. The principle is simple: keep debris away from the fine pores of ceramic or bio media, because once those clog they stop working. The real variable is not which media you buy, it is how often you are willing to open the filter - and that is what should decide your layout.

Water should meet the coarsest media first and the finest bio-media last.
30ppi foam is the practical shield in front of ceramic media; 20-30ppi works where the filter is oversized for the tank, and finer than 40ppi needs a pre-filter of its own.
Best clarity, and you don't mind maintenance: Layout 1, fine foam first, serviced every 2 to 4 weeks.
Least maintenance: Layout 2, coarse to fine, flushed all at once when it finally clogs.
Main chamber left alone for 4 to 6 months: Layout 4, a separate pre-filter cleaned every 3 to 6 weeks.
Complex multi-media stacks mostly sell media. They rarely outperform plain foam.

Complex filter media layouts tend to give the aquarist a feel-good factor without any significant increase in actual performance.

The wide variety of media on the market is the result of commercial companies looking for more ways to upsell hobbyists, and most do not make a significant difference in working efficiency. However, if you do choose to use a variety of different media, there are a few principles to follow.

Optimally, when using ceramic or bio media, we do not want the fine pores of the ceramic media surfaces to become clogged with organic debris, so ceramic media should be used after a layer of foam to filter out coarser particles. A 30ppi foam is the practical default for that shield: coarser than 20ppi lets too much through, and finer than 40ppi clogs fast enough that it needs a pre-filter of its own. If this foam layer becomes clogged, it can be flushed out without disturbing the subsequent layers of bio-media.

Why media surface area matters far less than the marketing suggests, and which media is actually worth buying, is covered in our guide to filter media. The biology underneath it - what the microbes are doing and what they need from you - is in tank cycling and biological maturity.

Layout 1: Fine foam first - best water clarity, most maintenance

The finest layer is placed on the first layer, this layer will clog quickly and requires regular maintenance (every 2 to 4 weeks) to prevent slowing down the flow of the whole filter. The middle foam layer acts both as a bio-media and a fine particle trap. The bio-media is kept free of large particles by being the last layer.

Pros:

Fine layer of foam prevents bio-media segments from clogging up.
Only the first layer has to be serviced regularly, the rest of the filter can be left undisturbed for long periods.
Great for stability of the bio-media's microbial community.
Fine particulate matter is captured well.

Cons:

Finer layer foam layer will clog quickly.
Clogging of the first layer will slow down flow for the whole filter.
Unsuitable layout for folks that are not regular on maintenance.

Layout 2: Coarse to fine - the lowest-maintenance canister filter media order

For people who are lazy and want to minimise the cleaning of the filter. The layout should start with the coarsest media and progress to the next finer media, with the last layer being the finest. This filter layout will take the longest to clog as the layers progressively filter out particulate matter, and will require the least maintenance. However, once clogged, you will need to flush most of the layers at the same time, which may cause some disruption to the microbial colonies.

Pros:

Less servicing required, filter will take an extended period to clog.
Fine particulate matter is captured well due to the mix of coarse and fine layers.

Cons:

Maintenance will likely require servicing of all layers at the same time.
Bio-media layers may clog more easily, and not have optimal water flow

Layout 3: Ceramic media only - never clogs, catches less

As all foam media will eventually clog, some hobbyists have used ceramic media exclusively in their filters. The large spacing between the individual pieces means that the filter will never clog completely. This layout is also less efficient at capturing particulate matter. While there is no direct mechanical capture of particulate matter by fine filter media, the bacterial biofilm still clumps particulate matter and debris. The coarse nature of the media means that clumps of detritus are more likely to settle in the tank than in the filter. In tanks where water changes are frequent, or where there is no significant generation of particulate matter, this filter layout may work well.

Pros:

Almost no maintenance.
No slow down of water flow due to large spacing between ceramic pieces.

Cons:

Fine particulate matter will likely settle on the tank substrate rather than filter.
Fine pores of the bio-media will clog more easily.
Best used in tanks with frequent water changes.

Layout 4: Pre-filter before the main chamber - what we run

This is a similar layout to layout 1, except that the fine foam layer is in a separate pre-filter chamber. The pre-filter chamber is separated from the main chamber to keep it accessible and should be serviced regularly. The pre-filter prevents larger waste particles from accumulating in the main chamber. This design allows the main chamber to operate undisturbed for long periods (typically 4 to 6 months, depending on bioload, filter size and the grade of pre-filter foam used), while the easily accessible pre-filter chamber is cleaned more frequently (every 3 to 6 weeks).

The finer filter foam used in the pre-filter easily filters out fine particles. This makes it easy to achieve high water clarity without disturbing the bio-media. Some filter models on the market come with integrated pre-filters. Pre-filters can also be installed separately before the main filter.

Pros:

Fine particulate matter is captured well, great water clarity.
Bio-media does not clog.
Bio-media layers are left undisturbed for extended periods of time, ensuring continuous stability of the biological system.

Cons:

Most filters on the market do not come with a build-in pre-filter.
Pre-filter needs to be serviced regularly.

A new filter also has to be seeded before it can do any of this - see how to cycle a planted tank.

In filters such as the Oase Biomaster range (shown below), the fine pre-filter foam allows the main chamber to run for 4 to 6 months between services. The pre-filter can be easily removed without touching the main chamber. This is the design we at 2hr Aquarist prefer to use on our own tanks.