The third type of filtration in the aquarium
is bio-filtration. Biological "filtration"
extends the sense of "filtration"
to include the varied uses made of dissolved
substances by living organisms, hopefully
by plants, but also by algae and by the mixed
bacterial community that forms the basis
of the biofilm that covers every permanently
wet surface in the aquarium. The "biological
filter" operating throughout the aquarium
takes ammonia and metabolizes it to harmless
nitrate. Though that's just one aspect of
the paths of energy and nutrients, it's more
convenient to think of biological "filtration"
in that context. So, though biological "filtration"
is actually more essential to the success
of your aquarium than mechanical filtration,
I've treated material about biofiltration
as part of the "Nitrogen Cycle" --and other cycles-- in the "Nutrient
Cycles" folder.
You can learn a lot about bio-filtration
in the aquarium by following some technological
developments in the wastewater management
industry. For example, there are some papers from a North Carolina University wastewater
conference that will introduce you to some of the wastewater
management uses of "bio-filtration."
