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Re: the grand eqn debate (was: More musing on water change.)

On 25 Jul 2002, at 23:21, various wrote:

> >Tyrone Genade wrote:
> >>On 25 Jul 2002, at 10:08, Wright Huntley wrote:

> >>The biochemist to the rescue... perhaps.

Well I said perhaps...

Firstly, I admit the mistake in the grossly over simplified 
mathematical example.:-(
But! your fish tank by virtue that it needs outside imput and removal 
of waster DOES NOT REACH EQUILIBRIUM. An equilibrium is possible 
between the keeper and the tank but that is where the buck stops. And 
this is a very tenuous eqm given our tendancy to go on holiday every 
now and then.

So far we have looked at the simple example of X waster being 
produced. This is far from the truth. The level of waste accumalated 
over various time intervals (as small as you like) will differ. Today 
you had a pinch more food, tomorrow that hornwort just suddenly 
collapses and dies, there is a phage virus taking out the bacteria 
causing more waste the next day and so on ad infinitum...

Waste will accumalate to the point where that mystical balance 
derived mathematicly for the simplified example does no exist and doe 

So what can be done?

Simple y% water changes will not stop the long term build up of waste 
be it in the form of NO3- or the bacterial sludge hiding in your 
filter (which is broken down into H2S, methane etc... by the various 
other bacteria). Every now and then you will have to do a MAJOR water 
change and syphon the UGF or rinse the box filter. This is standard 
fish tank maintenance and you all know it. You also no this because 
simple water changes don't do the trick.

So, to recap: 

1)no such thing as fish tank equilibrium (in tank I know off).
2)fishtank-fishkeeper equilibrium is possible but it does not rely on 
a simple y% water change.
3)fish tanks don't obey simple math, if they did someone would of 
worked out a fishtank maintenance relationship years ago and all you 
would have to do was enter the biomass of the fish, growth rate of 
the fish, how much food is added, the biomass of the plants, initial 
biomass of bacteria, growth rate of EVERY bacteria in the tank, how 
much light energy the tank gets per day, rate if water turn over, 
aeration, chemical analysis of the tank at every interval etc... 
Pretty much impossible for now.

Lastly, Scott Lewis, read the article you clearly have no idea what 
you are talking about.

Tyrone Genade
tgenade at sun_ac.za

P450 Lab, Biochemistry Department
University of Stellenbosch, 7602, South Africa
Ph: +27-021-808-5876, fax: +27-021-808-5863

"Seek your happiness in the Lord."
                  Psalms 37:4
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