[reefaddict]

Sempre Charles Delbeek, quindici ani fa:

Live rock contains a multitude of bacteria both on the exterior and
interior of the rock, some of which are the exact same as those found
in a seeded wet/dry filter. Hence, they are perfectly capable of
nitrification. When a fish passes ammonia across its gills into the
surrounding water, or defecates, these products do not simply seek the
wet/dry filter underneath the aquarium. They are, instead,
competitively utilized by whichever organisms come in contact with
them first and considering the high velocity flow recommended in a
reef aquarium, these are usually the rock, algae and invertebrates.
Algae growing on the live rock as well as various zooxanthellae
containing invertebrates (hermatypic), will rapidly take-up dissolved
ammonia. In addition, various heterotrophic bacteria in the system
will rapidly breakdown solid wastes and numerous invertebrates will
ingest solids such as feces. In turn, if ammonia is excreted by these
organisms, it may be rapidly consumed by algae and hermatypic
invertebrates situated on the rock.

The key word here is proximity. The nitrifying bacteria, even on the
rocks, are in for serious competition for nitrogenous waste. Still,
they do get some and, like their counterparts in the wet/dry filter,
they convert ammonia to nitrite, and nitrite to nitrate while
consuming oxygen. However, unlike a wet/dry filter, the nitrifying
bacteria on the rock are in very close proximity to anaerobic areas
within the rock. For this reason, the little bit of nitrate produced
at any given time can be immediately denitrified by facultative
anaerobes in the core of the rock, where there may be plenty of
organic material to allow the process to occur completely and
efficiently. In addition, algae and corals growing on the surface of
the rock can also use the nitrate in the small pulses they are
accustomed to using. However, if the level of nitrate in the water is
too high, the system becomes saturated and these natural processes do
not function efficiently. In this situation the algae and
zooxanthellae cannot use their nitrate utilization mechanisms to pull
the nitrate level down. Still, high levels of nitrate in the water,
combined with high water flow, can create a situation where incomplete
denitrification can occur which would tend to stimulate algae growth
on the rocks; desirable or undesirable. In this situation the wet/dry
filter functions as a nitrate factory. The presence of live rock can,
however, inhibit wet/dry nitrate production either partially or
completely, depending on the bioload (animals and feeding) in the
system.

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