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?