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#1
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Water chemistry & cakcium hydroxide addition.
Hello,
I keep a tanganyika-style tank, and wish to maintain water at high pH and high KH. I also come from a reef background, and there I used saturated calcium hydroxide solution as top-up water - this both maintained pH and KH, plus kept calcium levels high. Anyway, can I use calcium hydroxide as top-up water in my Tanganyika tank too? In sal****er I gather the calcium hydroxide works thusly: Calcium hydroxide releases OH- anc Ca2+. The carbonate buffering of the aquarium is shifted towards carbonate, and more carbon dioxide is sucked in from the atmosphere to counter the rise in pH. After equilibrum with the atmosphere has been reached, the end result is a net rise in KH, and a stabilization of pH at 8.3 (because 8.3 = (pKa + pKb)/2, where pKa and pKb are the log dissociation constants of bicarbonate and carbonate, and the carbonic acid concentration at these pH's can be approximated by zero). End result is the same as dissolving limestone with carbonic acid. Would it work the same in freshwater? As far as I can see it should, but I have been told that the resulting pH would be a little over 9, which if so seems to suggest that the pK's are different in fresh than salt water? |
#2
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Water chemistry & cakcium hydroxide addition.
"Mike Noren" wrote in message om... Hello, I keep a tanganyika-style tank, and wish to maintain water at high pH and high KH. I also come from a reef background, and there I used saturated calcium hydroxide solution as top-up water - this both maintained pH and KH, plus kept calcium levels high. Anyway, can I use calcium hydroxide as top-up water in my Tanganyika tank too? In sal****er I gather the calcium hydroxide works thusly: Calcium hydroxide releases OH- anc Ca2+. The carbonate buffering of the aquarium is shifted towards carbonate, and more carbon dioxide is sucked in from the atmosphere to counter the rise in pH. After equilibrum with the atmosphere has been reached, the end result is a net rise in KH, and a stabilization of pH at 8.3 (because 8.3 = (pKa + pKb)/2, where pKa and pKb are the log dissociation constants of bicarbonate and carbonate, and the carbonic acid concentration at these pH's can be approximated by zero). End result is the same as dissolving limestone with carbonic acid. Would it work the same in freshwater? As far as I can see it should, but I have been told that the resulting pH would be a little over 9, which if so seems to suggest that the pK's are different in fresh than salt water? If I remember my chemistry, probably.... Check the chemistry of Lake Tanganyika though and the requirements of the fish as it sticks in my head that the lakes are more sodium bicarbonate lakes and you might find bicarbonate or sodium hydroxide a better match. Bob |
#3
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Water chemistry & cakcium hydroxide addition.
You can use crushed coral as a substrate, excellent for higher ph. Also you
can add small sea shells to your filter. "Robert Flory" wrote in message news "Mike Noren" wrote in message om... Hello, I keep a tanganyika-style tank, and wish to maintain water at high pH and high KH. I also come from a reef background, and there I used saturated calcium hydroxide solution as top-up water - this both maintained pH and KH, plus kept calcium levels high. Anyway, can I use calcium hydroxide as top-up water in my Tanganyika tank too? In sal****er I gather the calcium hydroxide works thusly: Calcium hydroxide releases OH- anc Ca2+. The carbonate buffering of the aquarium is shifted towards carbonate, and more carbon dioxide is sucked in from the atmosphere to counter the rise in pH. After equilibrum with the atmosphere has been reached, the end result is a net rise in KH, and a stabilization of pH at 8.3 (because 8.3 = (pKa + pKb)/2, where pKa and pKb are the log dissociation constants of bicarbonate and carbonate, and the carbonic acid concentration at these pH's can be approximated by zero). End result is the same as dissolving limestone with carbonic acid. Would it work the same in freshwater? As far as I can see it should, but I have been told that the resulting pH would be a little over 9, which if so seems to suggest that the pK's are different in fresh than salt water? If I remember my chemistry, probably.... Check the chemistry of Lake Tanganyika though and the requirements of the fish as it sticks in my head that the lakes are more sodium bicarbonate lakes and you might find bicarbonate or sodium hydroxide a better match. Bob |
#4
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Water chemistry & cakcium hydroxide addition.
"Cam" wrote in message ...
Anyway, can I use calcium hydroxide as top-up water in my Tanganyika tank too? You can use crushed coral as a substrate, excellent for higher ph. Also you can add small sea shells to your filter. The entire tank is filled with limestone and limestone sand. That only very slowly raises pH to under 8, and really provides little in the form of buffering. Using calcium hydroxide raises pH, alkalinity, and carbonate hardness at the same time, and buffers pH to 8.3 (or it does in sal****er anyway - the issue here is if calcium hydroxide gives a different end pH in freshwater). This is not least important as some of my animals are borderline brackish. (Bizarre... All my posts from yesterday, e.g. the one first in this thread, appeared on Google Groups, and then disappeared again. Even the replies to my posts are gone. Did I somehow trigger a filter, I wonder.) |
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