I don't put anything in the water, since the water out of the tap is pretty clean to begin with.
One of the joys of living in Hawaii.
This brings up an interesting question which I have been pondering about for a while.
I got Malawi cichlids, which all experts agree that they should be in high pH water.
I really don't want to start putting stuff (even crushed coral) just for the sole purpose of getting the pH high.
The fish have been aclimated by the LFS for a while to the local water conditions, and I've verified that they do not do anything to the water out of the tap.
If the fish are fine from the LFS, no sense adjusting the pH???
The water out of the tap is already 7.6, so it's close to the 8.0 - 8.2 that's recommended for these fish.
The fish seem to be doing fine with no adjustment to the pH for several months now.