View Full Version : Quarantine - Salinity 1.023 to 1.009 - pH drop?
Sooners
10/02/2009, 05:09 PM
If you have a small 10g quarantine at 1.023, and you drop it to 1.009 for hyposalinity treatment with pure RO water, will that cause the the pH to drop or otherwise affect pH in and of itself?
kgross
10/02/2009, 10:13 PM
It will not directly effect the pH.
If you are not adding or subtracting H+, you are not effecting ph directly. The lower sg will equal less alkalinity so buffering capacity will be reduced. . What are your concerns?
Randy Holmes-Farley
10/03/2009, 05:45 AM
There may be an impact on pH due to the many ion-ion interaction changes that go on when diluting seawater. For example, the acidity of bicarbonate and carbonic acid are quite different in fresh water than in seawater, and so dropping the salinity could impact pH for those reasons. This is why, for example, putting baking soda in seawater at pH 8.2 drops pH but in fresh water at pH 8.2, it raises the pH.
You are also reducing the alkalinity on diluting seawater, typically, so all other things being equal (which they are not for the reasons mentioned above), you'd drop the pH a bit when equilibrated with your air.
In any case, if you are worried, just measure it, and if you need to raise it (say, if it is under pH 7.7), add a tiny pinch of baked baking soda. Don't do anything about it if you have not actually measured pH to be off. If it reads too high (say, over 8.5), just aerate more.
Sooners
10/03/2009, 06:35 AM
Thanks for the replies.
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