No salt mixes at 575ppm Ca. IO and Kent are comparable, but not the same. But either is fine, and based on price, go with IO. Have you yet come up with a reason to NOT use IO?? You keep asking about replacements, not sure what you find wrong about the salt.
Seriously, stop reading salt threads and buy want you want. Add it to your tank. If, after a long while, you come up with a reason it isn't working, look for salt threads again.
__________________
Brad
|