You can test before, but you need to "buffer" the water to get the proper readings. Some say before you add the salt. I would just add the salt and then test. You should be ok then after adding the salt, if not just add the proper buffer to get within normal limits...
32 gallon hex, 34 lbs lr
, Prizm protein skimmer, fluval 104, 1 maxi jet 750, 1 maxi jet 1200 ph
, current 40w 50/50 pc
, 1 NO
powerglo 19watt, 1 daylight NO
65w (equiv), two damsels, 1 green brittlestar, 1 peppermint shrimp, turbo snails, red legged hermit crabs, kenyan tree coral, leather coral, pumping xenia, mushroom coral, green star polyps, orange button polyps