Hi all, The issue is really to do with ammonia (NH3/NH4+). Ammonia is produced by all aquatic multi-cellular animals (fish, shrimps, snails etc.) following the digestion of proteins. <"
Any excess of amino acids"> are deaminated to form ammonia, which continually diffuses from the fish and shrimps gills into the water column.
<"
Ammonia is toxic"> at fairly low levels (well below 0.5ppm) so it is important that that ammonia is converted to the equally <"
toxic nitrite (NO2-)"> and relatively <"
benign nitrate (NO3-)">.
We need to remove the ammonia and nitrite as rapidly as possible, we can't allow their levels to build up.
It is different for the NO3, we are only going to get toxicity when we are into the hundreds of milligrams per litre (mg/L = ppm).
Nitrification is an oxygen intensive process and also reduces water hardness (acids are "H+ ion donors", and we've added three of them).
Non-planted tank
In an aquarium without plants biological nitrification is the process where a <"
specialised range of micro-organisms"> (mainly in the filter) convert NH3/NH4+ to NO3-, either via NO2-, or in the case of
Nitrospira <"
directly from NH3 to NO3-">.
This is where a lot of the discussion in forums etc gets side-tracked, because it looks on
- ammonia and
- the nature, and volume, of the biological filter media
as the important issues, where it
should be looking at oxygen.
Microbial biological filtration is <"nearly always limited by oxygen availability">. Assuming we have sufficient oxygen, NO3- will accumulate in the water column, and can only be removed by anion exchange, dilution or <"
anaerobic denitrification"> (the linked <"
Media set up"> thread has a lot more detail).
Planted Tank
The schematic below for photosynthesis is the most important equation for (multicellular) life on earth and gave us the oxygen we breathe
A planted aquarium increase <"
the potential for nitrification"> in three ways:
Compared to using plants, attempting anaerobic denitrification in a canister filter is such a bad idea, I can't actually imagine why any-one would advocate it as a viable option. There is a fuller discussion in the PlanetCatfish <"
Using deep gravel....."> thread, where not every-one is a planted tank keeper, and it dips in and out of various UKAPS threads.
cheers Darrel