get some ro water from somewhere or invest and get ro filter... you wont think twice after you get one....my lfs sells 5 gal of ro if i need in pinch couple bucks... i dont even touch tap water any more.. at least mine too much work too it...
i have access to RODI since i also have a reef, i dont have a gh test but i think its pretty low, and my KH is only about 1-2. i know, it makes no sense, and im reading my ph with a milwaukee probe. weird. my gh reads pretty low with dip-strips. people keep sps reefs here with tap.
i never did much have luck with cherries. so the gh/kh is more important that the ph? everything i know about water chemistry says that my water makes no sense. with kh that low there should be almost no buffering capacity and the ph should be neutral or less and the tiniest bit of anything should change the ph a lot, but, even a double dose of neutral regulator only gets me down to 7.5