The Dutch translation of this article is by DeepL Translate, it can be inaccurate, incomplete and probably with some of errors! But much better than Google Translate

7.1. Review of Media

Photo of author

Author : David Bogert

Published :

Time To Read :
5 minutes
Difficulty : Level 6

Excerpt :

For media inside any aquarium filter, foam, plastic pot scrubbers and K1 media were much better than ceramics, lava rock or pumice.
The first consideration when choosing a filter media is the ammonia oxidizing capability of the media.

Filter Media Ammonia Oxidizing Capacity

Three tests (24 ninety day runs total) of the ammonia oxidizing capability of various filter media were run. All three tests correlated remarkably well. The tests gave an “efficiency” number for various aquarium filter media.

The first number, the “efficiency from two tests” is the average ammonia oxidizing that 15 cubic inches (245,81 cm³) of media accomplished over a 90-day period. The second number is the “effective” surface area in square feet per cubic feet calculated from that test. The third number is the effective surface area in square feet per cubic feet calculated by simple mathematics. The correlation between the test results and the calculated surface area is very significant and means the testing was accurate.

Media“Efficiency” from two tests *“Effective” surface area ft²/ft³ ft²/ft³ from math“Effective” surface area m²/m³m²/m³ from math
Fluidized K1 medianot tested600na1980na
30 PPI foam1734040011221320
Pot scrubbers1428080924264
Static K1 media13260200858660
20 PPI foamnot tested220180726594
Aquarium gravel6120120396396
Blue Matala pads5100120330396
Eshoppe bioballs510060330198
¼ to ½ inch lava rocks36060198198
Biohome ultimate2403013299
Ceramic rings24040132132
* average ammonia oxidizing that 15 cubic inches (245,81 cm³) of media accomplished over a 90-day period

The higher the number the better the media. So foam is the best static media and ceramic rings are the worst media for canisters by this test and by math calculations. Since foam must be exactly cut to the proper size to prevent flow around pot scrubbers and K1 are much easier to use successfully.

Note that for the metric system simply multiply any of the square feet per cubic feet numbers by 3.3 to get square meters per cubic meters. For the metric system 100,000 f²/f³ thus equals 330,000 m/m³ or 330 m²/liter .

Photo of K1 aquarium filter media
K1 filter media
image of Plastic Pot Scrubbers
Plastic Pot Scrubbers

What this can translate to is illustrated by the number of fish a typical canister can handle stocked with some of these media:

  • Foam – 35 five-inch (12,5 cm) fish
  • Static K1 media – 20 five-inch (12,5 cm) fish
  • Ceramic rings, Matrix – 4 five-inch (12,5 cm) fish

These numbers reflect a canister which will give a hobbyist crystal clear, bacteria free water which in turn will give one very healthy fish. These are some huge differences.

Click on this link for the test:

7.1.3. Filter Media Test

Yellow Parrot Cichlid
Yellow Parrot Cichlid

Surface Area Calculations

Note that the “surface area foot² per foot³” is generally based on simple math, not on the claims of the manufacturers. The calculations are:

BiomediaDiameter of pore in inchesX= Surface area of a sphere in inches²Y= pores per inch²XxY=ZZx12= surface area foot² per foot³Effective surface area
60 ppi foam0.0160.00082161732076800
40 ppi foam0.0250.0018641151380500
30 ppi foam0.0330.003626971164400
1/8 inch gravel0.1250.04851224288140
3/16 inch gravel0.1880.11114916.5198100
3/8 inch gravel0.3750.444198.4510150
1/2 inch gravel0.50.785863620
Calculating surface area of filter media

The reduction of the figures in the final column reflect the realities of the situation. For instance, only about 40% of the foam cell is surface, 60% of the cell area is void, which allows great water flow but doesn’t give surface area.

These math calculations were tested and the tests generally followed the results of the math. The only significant inaccuracy was that pot scrubbers were much better than math calculations predicted.

Aphanotorulus ammophilus L 94 pleco
Aphanotorulus ammophilus – Pleco – L94

Because of reticulation, flow and free volume considerations the surface area calculations and chart above can be superseded. Extrapolating from the testing and giving aquarium gravel the most dependable surface area calculation, gives the following “effective surface area” by media. This is the surface area which should be used for calculating the required volume of filter media for a given weight of fish.

Biomedia“Effective” surface area ft²/ft³“Effective” surface area m²/m³ft³ to get 5ft²m³ to get 0.46m²ft³ to get 100ft²m³ to get 9.29m²
Fluidized K1 media (60% loading in sump)5401782160.453209.06
30 PPI foam in canister or sump3401122250.7150014.16
30 PPI foam powerhead operated sponge3401122250.7150014.16
30 PPI foam air operated sponge30099029580
Plastic pot scrubbers28092431620
Static K1 media26085833660
20 PPI foam in canister or sump26085833660
20 PPI foam powerhead operated sponge26085833660
20 PPI foam air operated sponge23075938751
Powerhead operated undergravel filter140462621240
Aquarium gravel in canister or sump140462621240
Air operated undergravel filter120396721440
Blue Matala pads120396721440
1/8 inch garden pumice or perlite100330861720
Bio balls100330861720
1/2 inch lava rock601981442880
Seachem Matrix601981442880
Biohome Ultimate401322164320
Ceramic rings401322164320
Ceramic balls30992888.165760163.11
Expanded clay pebbles30992885760
Cubic inches to get 5ft² = (5/E.A.)x1,728 100ft²=(100/E.A.x1,728)

Note that for the metric system simply multiply any of the square feet per cubic feet numbers by 3.3 to get square meters per cubic meters. For the metric system 100,000 f²/f³ thus equals 330,000 m²/m³ or 330 m²/liter.

Ammonia Oxidation versus Water Clarity

What is often missed in these calculations is that it is easy to oxidize ammonia. Oxidizing ammonia only requires on the order of five square foot (0,46 m²) of surface area for one pound (454 gram) of fish per testing and per the literature. But testing and the literature support the fact that crystal clear water requires somewhere around 100 square foot (9,29 m²) of surface area per pound (454 gram) of fish. And crystal clear water is healthy, disease free water.

Blue Dragonblood Peacock
Blue Dragonblood Peacock

Manufacturers’ Claims and Instructions

The claims of many ceramic, pumice and sandstone media manufacturers are based on something called the BET nitrogen infusion method. It measures the amount of nitrogen which permeates a media and adsorbs onto the surface of the media in a single molecule layer.

Since the nitrogen molecule is a couple of billion times smaller than a beneficial bacteria cell this is obviously a very misleading statistic. If a beneficial bacterial cell can’t even get to a surface, let alone form a film on it, the surface is useless. The tiny pores in many media are thus simply of no use.

Another concept which is pushed by manufacturers of some filters is that media needs to be replaced on a regular basis. Some HOB manufacturers say their cartridges need to be replaced every month. There are canister filter manufacturers that say the ceramic bio-rings and the foam in their filters need to be replaced every six months.

This is just ridiculous. Pure and simple profit motivated Hogwash!!!! Cartridges are easily cleaned when they plug and can be reused for years. Foam will last five to ten years while ceramic or plastic media will last for twenty years or more.

Aquarium Fish Pseudotropheus demasoni
Pseudotropheus demasoni

Belief Perseverance Effect

Experience on social media has shown that the table above and the testing which produced it will not be believed by 90% of the hobbyists that read it. They will fiercely defend their favorite media (Matrix is probably the single most popular filter media and easily 90% of all biomedia used is either expensive Matrix, Biohome or a ceramic media) and no one will be able to change their minds.

If anything, heavy, slick marketing and the “power of popularity” will make them more intransigent. If presented with test data and logical, common-sense proofs of the data, they will rationalize the experiments away and then rationalize some more. This is called “belief perseverance effect,” something we all fall prey to, and there is no point in fighting it.

“Nothing dies harder than a lie that people want to believe”


The numbers are accurate, and that fact is proven in the links below.

Peacock Gudgeon
Peacock Gudgeon

For more information about filter media click on these links:

7.1.1. Filter Media Costing

7.1.2. Function of Filter Media

7.1.3. Filter Media Testing Filter Media Ammonia Oxidation Test Filter Media Water Clarity Test