what does "stale pH" mean?
to the original poster, the gist of what xander is saying is correct. go with a system that will have consistent pH and avoid major fluctuations. this is also somewhat dependent on the species of gar that you are keeping. Florida, spotted, tropical, alligator don't seem to be as picky as Cubans, and to a lesser extent longnose and shortnose.
either way, too low of a pH does have reduced buffering capacity, so you will want to make sure that, especially in a SAmerican predatory tank, that you have good water quality and low fluctuation. good luck--
--solomon