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Re: Musing on water change

Roger Hawthorne wrote:
> I'm glad I'm not a mathematician. Possibly not even a speller.

:-) You share the puzzlement of some of us at the bizarre definitions of 
things like equilibrium that have been posted here, perhaps?

Beer can certainly upset one's equilibrium, if consumed in sufficient 
quantity, but chemical equilibrium is when a balance has been achieved 
between two opposing reactions or activities. In the partial-change 
scenario, if the poop in equals the poop out, averaged over some 
reasonable time interval, then poop quantity settles out, roughly 
centered around some equilibrium value after a while. For 25% weekly 
changes, it is 3.5 weeks worth of poop accumulation that is that balance 
point. It oscillates up and down by 0.5 weeks worth after that.

If we start with a sterile, clean tank, the poop builds up, 
asymptotically approaching an end value, and then gently oscillates as 
poop accumulates for a week and then is suddenly removed on Sat. Poop 
removal and addition have reached their equilibrium value, but 
mathematically they never really do reach it. The errors just get too 
small to matter.

Tyrone probably argues that to reach the wall you must first walk half 
way to the wall. Then you must go the new half way, ad infinitum, never 
reaching the wall. Ergo, there is no wall! ;-)

> Our municipal water is very soft. Our well water is carbonic.
> Wouldn't the water you add have a lot to do with how often
> a change is required? Certainly some reidues left over are
> less detrimental than others. Anyone have info on that? 

The frequency of change is determined by many factors, but your starting 
water is one of the less important of those. The change is to give the 
fish a chance to live outside the toilet, to paraphrase Charles, and the 
new water should be an improvement or the change would be a bad thing.

My suspicion is that there are less good things in old water than some 
have reported, but that changing too much at once has caused some kind 
of shock. Shortening the change interval can help that, and flow-through 
systems are the end point of that process -- probably as good as it gets.

> The Killies I saw ( certainly could actually be fundulus or a
> similar fish ) in Cuba seemed to prefer the very end of a
> body of water, opposite the inlet. Even when I set up my  
> camcorder and left, they spent most of their time in the mulm.  
> Maybe for instant hiding. Yet if I approached, they sped off
> in a different direction. Few dropped down into the mulm to
> hide. Maybe that is where they spawn? I should have asked  
> Barry. These guys were not afraid of the saltier areas either.

Estuarine fish are really fun to watch. If you realize the changes in 
salinity they willingly swim through, it is amazing at how easily we can 
damage other killies with a simple sudden drop in tds. Maybe someone 
here on the list can offer an explanation (or guess) as to how they 
adjust or protect themselves from osmotic shock.

I wish I had been more observant when I lived on Tampa Bay, back in my 
early years. I was more into catching than watching, in those days.


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

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