As Brad mentioned, around 8 or 9dkh as a top end. I have yet to figure out how to do that with my reactor, as not matter what I set it at, the tank alk. stays at 13dkh.
Also like Steve, there are some in the same threads that dispute these claims. I think more time is needed on this, as I remember when it was said we were running our alk. to low at 8dkh and needed to run at around 12dkh to help the sps colour.
Perhaps this was a self preservation move from the sps corals, as the alk. was raised.
