[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: Cycled Tank Definition

Matthew Mason wrote:

> What is the definition of a cycled tank?

I suppose that 99% of the time that an aquarium keeper refers to a tank as
"cycled" they mean only that the tank is more than a few weeks old and
doesn't have trouble with ammonia or nitrite.  Many would also mean that
the tank experienced a succession of ammonium and nitrite spikes and
afterwords contained nitrate as the major nitrogen nutrient.

>         -Does this definition include the water column?

Water tests are usually done on samples from the water column, but the
terminology is applied to the tank as a whole.

>         -Does this definition include a complete, thriving colony of
> ammonium/nitrate
>           consuming/converting bacteria?

We do tend to assume that the presence of nitrate requires the presence of
the bacteria that make it, but we don't measure the size or viability of
their population directly, so I don't suppose it's part of the definition.

>         -Is a cycled tank one that has just been set-up, new water, but
> contains a sponge from a cycled
> tank?

The setup needs to exist long enough for you to measure nitrate before
you can call it "cycled".

>         -Does a cycling tank _need_ plants, do they help the process be
> completed faster, are there
>           disadvantages to cycling with plants?

If plants are using ammonium, then bacteria aren't; the ammonium
concentration is lower than it would be in the absence of plants and the
bacteria population grows more slowly.  Advantage: the ammonium
concentration is lower.  Disadvantage: the bacteria population is smaller,
but then, so what?

[snip] This is a serious post, so, serious responses only please.

Shucks.  I had a really hilarious writeup going, and had to pitch it when
I got to this point :).

Beyond the basic nitrogen cycle, there probably are a lot of other events
that occur while an aquarium is breaking in.  My simulations, as weak as
they are at this point, show changes continuing nearly 6 months after a
tank setup.  I don't usually run past that point so it's possible that it
might show significant changes at even later times.

For example (not a simulated event)... Lots of people see a diatom "bloom"
early in their tank setup.  Why? and why does it usually disappear on its
own after awhile?  Another example (this from my model)... Are there
regularly deep, temporary drops in substrate oxygen levels after a tank is
setup? If so, why, and why do conditions recover?  While I'm at it, yet a
third example... I've heard people complain (bitterly, in fact) of
ammonium spikes occuring with no evident cause months after an original
tank setup, with the implication that this happens consistently if you use
a UGF. Does it? If so, why?

Roger Miller

In Albuquerque, where spring is often a good time to be someplace else.