Patience is the key to saltwater aquariums! I say wait at least a month or so. If the fw
tests you found don't work, maybe your LFS
will test your water for you. You can always change stock ideas later.
It suggested that to have a mandarin goby, you need a tank with at least 75 lbs of live rock that has been established no less than a year and a half. They're really pretty fish, but they should be left in the ocean IMO
. They're hard to feed and keep alive. Most dragonets are that way. (Mandarin goby isn't really a goby, it's a dragonet.)