3 Stages of Filtration and What They Do.

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The basics of filtration (in a nutshell):

Mechanical - removes free floating particles from your water
Biological - removes the poisonous nitrogenous waste from water (Ammonia, nitrites) and converts to Nitrates
Chemical - removes impurities from the water, and to some extent, polish the water. There are products to remove discolouration, odors, nitrates, phosphates, copper, hardness and others

The various filter manufacturers utilise different media types to achieve each stage of filtration.

Mechanical Media - often includes coarse sponges, filter floss/wool (particularly good for water polishing too), the ceramic white cylinders (pre-filters) aka ceramic noodles.

Biological Media - Beneficial bacteria will grow on any surface in the aquarium, and generally speaking, the more porous the media, the easier it is for a bacteria colony to grow and replicate. Some media types used today are Bio-balls, Bio-Wheels, Ceramic noodles. Bio-Max from Fluval is a highly porous cyclinder. Substrat (Pro) from EheI'm are small, highly porous balls. Other manufacturers use smaller ceramic porous elements for this. And some hobbyists also use terracotta pots

Note: Many sponges used in mechanical filtration will also serve a double purpose, whereby bacteria will grow on the sponge as well as the dedicated media.

Chemical - the most common chemical media is carbon, it has a short life (usually around 4 weeks) and absorbs impurities from the water such as tannins (leached from driftwood), medicines and odours. Also available are products that absorb phosphate, nitrates, copper and there is also a product called a water softening pillow that can be used to reduce General Hardness (GH)

Is one type of bio media better than another? e.g. are bio-balls better than substrat?
Yes and no. In sufficient quantities, all media will do a good job.

How do I organise my filter?
In my EheI'm Classic canister, the media is setup as follows (in order of the way the water flows through the filter)

Pre-filter (ceramic noodles) -> Mechanical (coarse sponge) -> Biological (EheI'm Substrat Pro) -> Mechanical (fine filter sponge) -> Chemical (if required, at present I don't run any chemical filtration)

Note - This is not the only way to setup your media, and you do not have to have the pre-filter. Where ever possible, I strongly recommend that free floating particles be trapped prior to biological media, this will keep your bio media cleaner. i.e. by using a pre-filter or coarse sponge first.

In some filters, I recognise that this type of setup is not always possible.

To all: As this is an information only post, it has been closed, if you feel anything should be added, please pm myself or a moderator and we will update the thread.

I hope that helps.

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