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/m³||m²/m³ from math|
|Fluidized K1 media||not tested||600||na||1980||na|
|30 PPI foam||17||340||400||1122||1320|
|Static K1 media||13||260||200||858||660|
|20 PPI foam||not tested||220||180||726||594|
|Blue Matala pads||5||100||120||330||396|
|¼ to ½ inch lava rocks||3||60||60||198||198|
|* 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 .
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:
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:
|Biomedia||Diameter of pore in inches||X= Surface area of a sphere in inches²||Y= pores per inch²||XxY=Z||Zx12= surface area foot² per foot³||Effective surface area|
|60 ppi foam||0.016||0.0008||216||173||2076||800|
|40 ppi foam||0.025||0.0018||64||115||1380||500|
|30 ppi foam||0.033||0.0036||26||97||1164||400|
|1/8 inch gravel||0.125||0.048||512||24||288||140|
|3/16 inch gravel||0.188||0.111||149||16.5||198||100|
|3/8 inch gravel||0.375||0.444||19||8.45||101||50|
|1/2 inch gravel||0.5||0.785||8||6||36||20|
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.
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/m³||ft³ to get 5ft²||m³ to get 0.46m²||ft³ to get 100ft²||m³ to get 9.29m²|
|Fluidized K1 media (60% loading in sump)||540||1782||16||0.45||320||9.06|
|30 PPI foam in canister or sump||340||1122||25||0.71||500||14.16|
|30 PPI foam powerhead operated sponge||340||1122||25||0.71||500||14.16|
|30 PPI foam air operated sponge||300||990||29||580|
|Plastic pot scrubbers||280||924||31||620|
|Static K1 media||260||858||33||660|
|20 PPI foam in canister or sump||260||858||33||660|
|20 PPI foam powerhead operated sponge||260||858||33||660|
|20 PPI foam air operated sponge||230||759||38||751|
|Powerhead operated undergravel filter||140||462||62||1240|
|Aquarium gravel in canister or sump||140||462||62||1240|
|Air operated undergravel filter||120||396||72||1440|
|Blue Matala pads||120||396||72||1440|
|1/8 inch garden pumice or perlite||100||330||86||1720|
|1/2 inch lava rock||60||198||144||2880|
|Expanded clay pebbles||30||99||288||5760|
|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.
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.
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.
The numbers are accurate, and that fact is proven in the links below.
For more information about filter media click on these links: