[FragIt Dan]

I would expect there will be no Mg in either baking soda or CaCl (anhydrous or otherwise) unless it says on the bottle (bulk would be really unlikely). I would suggest you are either making the same mistake with two test kits and getting an erroneous reading (not likely), or your WC water has high Mg levels. It's easy to figure this out... just test the new ASW before you do your water change. If you are really wanting to verify things, test your tank water just before and maybe an hour after your WC along with your new ASW. You should be able to predict what your tank should be at after the WC.


Dan