Using a microscope to take a look at the internal structure of some common types of filter media. Please click 'show more' for all information on media, time stamps and worldwide links (where available).
Microscope used: http://geni.us/IyFI0m4
Good biological filter media needs to be receptive to bacteria, have a varied internal structure and last for a very long time if it is to support aerobic and anaerobic bacteria and have a chance of providing full cycle filtration (reduction in nitrate).
It generally falls into 4 categories (for static filters):
1 - PLASTIC- avoid for a static filter as the surface area is so low. Poor receptiveness to bacteria.
2 - NATURAL ROCK - can vary wildly in usefulness and may raise pH (white pumice). Varied receptiveness to bacteria but generally good.
3 - CERAMIC - made from clay dust. Quality of structure and hardness can be very varied depending on type. Relatively receptive to bacteria even on/in poor quality media.
4 - SINTERED GLASS - made from sand and powdered glass. Generally very hard but quality of internal structure can vary depending on mix used. Very receptive to bacteria.
Filter media in order of appearance:
SCORIA (lava rock): http://geni.us/daKf8n1
Scoria is commonly known as lava rock since it is an inert, natural volcanic rock. It is relatively heavy and although the outside may look extremely porous and good for bacteria to colonise the internal structure is largely inaccessible so as a filter media it is not ideal but it is cheap.
WHITE PUMICE: http://www.filterpro.co.uk
Volcanic rock which generally has good hardness, accessible internal structure but quality can vary. Drinking water quality pumice has best structure and quality but all white pumice has a high pH (generally around 8.0) making it really only suitable for marine, koi, goldfish, livebearers and Malawi / Tanganyikan cichlids.
Varied quality white pumice is commonly sold under different names by some manufacturers with no warning about pH.
Avoid if it is poor quality pumice which contains a large amount of grey / black stones as it will generally be micro porous and will quickly clog up.
Very hard, rough ceramic media which has good external surface area but poor porosity. Works well even in dirty filters as it does not clog easily (due to poor porosity). Very cheap = good budget choice for pond filters.
CHINESE CERAMIC - really poor quality media which is brittle, has poor internal structure, poor accessibility and will break down quickly in any sort of water flow. Unfortunately this is for sale all over the internet - avoid.
An inert, sintered glass media which is made in various sizes and has varied pore structure and accessibility for use in different types of filters.
Some types have added trace elements fused into the structure which are specific to the needs of bacteria and that allows the media to work even harder to provide full cycle filtration (reduction in nitrate) as long as plenty is used.
Marine version also available which has added effect of boosting coral health (due to trace elements / bacterial activity?).
As far as I know it is made by using a fine sintered glass mix with added bicarbonate of soda which causes mix to fluff up and be very light prior to firing in kiln.
pH (8.0+) is definitely an issue as is the brittleness of the media but the internal structure is very good.
00:00 Intro and explanation of what makes a good filter media + showing microscope used for video
03:30 Types of filter media to be examined
05:43 Looking inside media with microscope (300x)
09:45 How hard / long lasting is media?
12:35 Damn, I wasted how much on this muck from China?
16:35 Notes on surface area
Aquarium and Filtration Playlist: https://goo.gl/yg174k
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Zomei Z666 tripod: http://geni.us/1a1af3
Manfrotto MTPIXI-B PIXI mini tripod: http://geni.us/87f7
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