Ammonia is still being produced. The fish produce it
and so does food that rots. With more live rock, and
more live sand, you have more critters there to eat
uneaten food. If the food is caught in a filter it
tends to be less available for critters to eat it,
thus bacteria convert it into ammonia. Amphipods
often live well in such a filter, but the uneaten
food is put to better use if it is spread out in the
live rock, and live sand. Spaghetti worms are great
they take the food down into the sand, and this
helps feed the low oxygen bacteria, thus reducing
the nitrites and nitrates. Nitrification converts
nitrites into nitrates, but denitrification converts
nitrites into nitrogen, and nitrates into nitrites.
It takes longer for them to convert nitrates into
nitrogen, than it does to convert nitrites into
nitrogen, thus if the aerobic bacteria keep quickly
converting nitrites into nitrates, it makes it
harder for the low oxygen bacteria to keep up with
denitrification.

Wayne Sallee
Wayne's Pets


Add Homonym wrote on 1/29/2007 1:52 PM:
Been running my systems with no mechanical or chemical filtration for
some time, relying soley on live rock and sand for bilogocal filtration.

It works quite well.

My current system keeps nitrogenous waste levels at zero (or close
enough that none of my tests detect them)
ammonia, nitrite, nitrate, all 0.

Prior to this, I had sponge filters and some charcoal in a hang on tank
power filter. Ammonia and nitrites would be 0, but nitrrates would
fluctuate between 5 and 20. (*I still had the DSB and live rock at that
time)

What I don't get is this: It was explained to me that the problem with
intense biological filtration is that it works to well, hence the
nitrate buildup. That makes sense. But if you slow things down, relying
only on live rock and sand for the first two stages, so that the
anaeobic bacteria in the sand and rock can keep up with killing the
nitrates, why do you not see at least a slight rise in ammonia and or
nitrites?

I suppose i should just be happy that it works, but I don't entirely get
why...