[kgf12345]

http://www.mchportal.com/fishkeeping...chemistry.html

"Take the example of a hobbyist making a water change using tap water with a pH of 6.5. Additives (chemicals) are subsequently added to the water to bring the pH back up to 8.5 for the African cichlids in the tank. In such a case it is well possible to find some of the fish dead next day. Why?

The fish were accustomed to a certain H+concentration. Then, suddenly, they are facing new water coming in their tank, which only contains one hundredth of the normal H+. This is a shock by itself, a very serious shock. While in stress, the fish try to adapt to the new situation when suddenly something is added in the water which creates a new solution with 100 times more H+. No organism can adapt to this sort of fluctuations!! "

η αλλαγη του ph αυτη καθαυτη ισως να μην εχει αμμεση σχεση με τους θανατους αλλα το οσμοτικο σοκ που μπορει να προκαλεσει(μαλακο νερο--->σκληρο νερο) εχει...
συν οτι με την αλλαγη Ph το αμμωνιο μπορει να μετατραπει ξανα σε αμμωνια....

http://www.oscarfish.com/article-hom...-ph-shock.html

"We are all aware (or at least should be) of the effect pH has on the toxicity of ammonia. At a lower pH, ammonia is converted into ammonium, which is not toxic. As the pH increases, ammonium is converted into ammonia, which is toxic. What is less known is that pH has the same effect on other toxic substances such as chromium, mercury, copper, and iron.

As the pH falls (solution becomes more acidic) many insoluble substances become more soluble and thus available for absorption. For example, 4 mg/L of iron would not present a toxic effect at a pH of 4.8. However, as little as 0.9 mg/L of iron at a pH of 5.5 can cause fish to die.
It is these effects that present the myth of “pH shock”. It is not the change in the pH itself that causes issues thought of as “pH shock”. It is the physiological effects associated with an abrupt change in TDS and/or the synergistic effects of pH increases, or decreases, on toxic compounds within the water.

Evidence of this can be achieved by observing planted tanks with CO2 supplementation. These tanks can experience wide swings in pH over a 24-hour period with no ill effect on the fish, especially for those who turn off their CO2 regulators at night. Why can the pH change in these tanks without impacting the fish? Because carbon dioxide is influencing pH without affecting the amount of TDS in the tanks."