I would just like to say, you guys are all switching salts for one test done on it. To test salts like that you would need say 8 tanks for each type of salt. Each tank would have to have salt come from a different bucket of the same salt.
Just like everything else, products do go bad, depended on packaging and storing. The salt you bought could just have been bad.
I'm not here to sell IO salt but;
I've been in the hobby now for 6 years, the most tanks i've had running at once was 6. All with IO salt.
Only once did i have a big cynao bacteria outbreak. I figured it out to be a plugged filter causing a nitrate spike and to little flow in the tank, plus i had CC in the tank. As soon as i fixed the problems it went away. I still use IO salt to this day.
I bet all the salts out there are relatively the same. I would have to see a chemical makeup of each to change my mind.
Does anybody know the chemical makeup of each brand of salt?