Re: Why is list partcipation waning (and Cycling)

[Larry Jones <ljones at usc_edu>]

On 8/31/03 2:27 AM, "Aquatic Plants Digest"
<Aquatic-Plants-Owner at actwin_com> wrote:

> Re: Why is list partcipation waning (and Cycling)

> Can I ask one question though:  When should I add a sizable fish load:
> right away or gradually?  I've always done it gradually, but that was
> when I was actually cycling the tank.

I thought I would stop lurking for a minute. I have lurked on this list
since undergrad, so since around 1993-94. There seems to be much
misunderstanding about Nitrogen in planted and fish only aquaria. One major
error in thinking is that a "cycled" tank can accommodate any load of fish
and their wastes. A balance will be established between the amount of
bacterial food (ammonia, for simplicity I will just use ammonia/NH3) and the
number of consumers/bacteria. If you have a stable number of fish and feed
them the same amount of food you will have a stable amount of bacteria. If
you suddenly add a large number of NH3 producers ie fish you will have an
excess of NH3 until the consumers can multiply enough to take advantage of
the new food supply. In the short term you will have elevated levels of NH3.
Also if you return to the original number of fish you will have a deficit of
NH3 from the view of the bacteria therefore many will starve and die and you
will end with about the same number of bacteria you had before you added the
extra fish. Plants that are growing well also act as consumers of NH3. So
now you will have even less NH3 available to your bacterial consumers so
even more will starve. When your plant growth is optimal there may be no
measurable Nitrogen. And for those not in the know the "N" in NH3 is the
symbol for Nitrogen. So to jump to the question, I suppose it depends on
what you mean by sizable, and how heavily you are supplementing your
aquarium with nitrogen. And of course how large your aquarium is. In your
case you state approx 80gal. If you have rapid growth where you are tossing
out 6in cuttings off your stem plants weekly I wouldn't be worried about
adding 30-50 tetra sized fish. Of course on a side note I would worry about
introduction of disease. And I would still monitor the NH3 levels. If your
tank is not so heavily planted or the plants are not growing so fast, I
would add fish more gradually and still I would monitor the NH3 levels and
be ready for water changes as needed.

Another plus about NH3 in heavily planted rapid growth aquaria is that with
co2 supplementation and soft to moderately hard water the pH will be acid or
close to neutral. This will keep the bulk of the NH3 in the less toxic NH4+
form and keep the fish less stressed.

Well I am tired and back to lurk land I go.

Larry Jones
ljones at usc_edu