Re: [Killietalk] Couple of questions

[LeeH920226 at aol_com]

In a message dated 2/1/06 11:03:18 AM, barbax66 at peoplepc_com writes:

<< think we can have a case of over generalized information here. ken stated
his died from abrupt water changes. Perhaps TDS shock? Breeding will only
occur with frequent partial water changes from my experience. In fact after
water changes eggs were laid frequently.
 >>

Water changes can kill fish and lack of water changes can kill fish. That is 
an oversimplification that will further confuse those who are trying to 
understand the principles. The details are relatively simple, but must be 
understood. Think of water changes as flushing the toilet. After all everything that is 
fed to the fish stays in the tank as waste products until flushed out. Those 
include not only toxic materials that are harmless at low levels but toxic at 
some level. It also includes growth inhibiting hormones, etc., which may not 
kill the fish but stunt them and repress breeding behavior. So the answer to 
that is change the water. However, fish are totally at the mercy of their 
environment and that includes not only toxic materials but also the effect of those 
dissolved ions that influence osmotic pressure. The osmotic pressure of the 
solution is important because a pressure is created across any semipermeable 
membrane including all the cells of the fish. If there is a sudden change in the 
osmotic pressure, the cells may explode or collapse due to that pressure if the 
change is too great. The gills are particularly sensitive to those changes. 
Fish can adapt to a wide variation in osmotic pressure if it is gradual. So the 
changes must be minimal and gradual. So the answer to that dilemma is more 
frequent water changes so the tank does not have an opportunity to become 
greatly different from the replacement water. Another thing about water changes that 
can kill fish is the presence of chlorine or chloramine in the replacement 
water. I cannot emphasize enough the need to dechlorinate and test. Water 
companies are often prone to over chlorinate in flood times. That is good for us 
because it reduces the chance of E. coli and other pathogens. But it is not good 
for your fish.

Lee Harper
Media, PA
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