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Re: More musing on water change.

Tyrone Genade wrote:
> On 25 Jul 2002, at 10:08, Wright Huntley wrote:
> The biochemist to the rescue... perhaps.
>>Charles n Sue Harrison wrote:
>>>There is no equilibrium. and that is a common thought, that there
>>>must be.  
> No. And I will show why this is wrong but only after I give Wright a 
> good flaming... (how rare)
>>OK, Charles. Can you show me the arithmetic that demonstrates that?
>>If the added poop/concentration each week is *less* than that
>>contained in 25% of the total volume, you removed more than was added,
>>with a 25% change. How does that eventually reach a solid sludge
>>stage? Sounds like a classic partial dilution to me.
> The fish produce for arguements sake 10 mg/ml of waster per week. 

I suspect you may have meant a total of 10mg/L per week? Lets assume it 
is more like 1 gram in a 100L tank. Doesn't change the principle, anyway.

> does a 25% water change. Now there is 7.5 mg/ml waster left. One week 
> later and now there is 17.5 mg/ml waste. 25 (%) water change and then 
> there is 13.125 mg/ml... 

You might read what I actually wrote, instead of making assumptions. 
Note that 13.125 is way less than twice the 7.5 of the previous week and 
it will continue to asymptotically approach a situation where the 
removal is 10 (whatevers) per week, and the contaminants are oscillating 
between 30 and 40  each week. If you remove exactly as much as is added, 
I fail to see how you can increase the concentration any more.

Minus 10 for Tyrone. :-) Engineering still works.


"Deport all the product-liability lawyers to Iraq;"
                                 -- Dave Barry --
       [Best suggestion of 2002, by far...]

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