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?

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

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
.. .

"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

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.)