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Old 01-22-2007, 12:33 PM   #1 (permalink)
ed seeley
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Question Experience with pH crashes; Do they really happen?

Hi everyone,
This question stems from a discussion in a Killifish mailing group where one of the members had suffered a fish kill that he said was due to a pH crash.
He had measured the parameters in his tank after the die-off. His pH had dropped to 4.5 from the usual 6.5. He was using RO water with a pH 6.5 buffer.

He got lots of advice from the other members about buffering his KH, not just using a pH buffer, nut adding more KH to the water. Products to raise the KH were said to be 'essential'.

Personally I use RO water with Kent RO right, and relayed my experience of using that and maintaining my tanks with a KH of zero. This is with no added CO2, Fermented CO2 and Pressurised CO2 on various tanks.

My questions are these;
  1. Do pH crashes occur and what tank conditions are typical when they do?
  1. What causes pH crashes?
  1. Is it the pH crash that causes fatalities or are pH crashes merely a product of other problems in the tank that have caused fatalities?

In other words, do pollutants build up, poison the fish, but then get broken down by the filter producing acid that drops the pH and then you turn up the next day to a tank with a lowered pH and dead fish and, measuring the parameters, find the pH as the obvious change and blame a 'crash'?

I'm not convinced that a pH drop, in itself, would be so disastrous. I think something must cause the pH to drop and what is this? Why does it seem to have such drastic effects? Is it the often trotted out 'running out of buffers'? If so why does my water, with no measureable buffers, not crash constantly and all my fish die?

Please add all your experiences and thoughts.
I am looking for any first hand evidence of, and dealings with, pH crashes, not the heresay and myth that is spread around.

What about those of you, who, like me, use water with almost no buffer? Have any of you had a crash?
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