owner isn't really telling the truth there. There seem to be big differences in salt, but as to which one is better.... not gonna touch that one. Search the forum here and you'll find tons of discussions about that. There's no "consumer guide" for salts because what is "good" is really subjective. The closest thing is a "study" Eric Borneman did on different salts, but even that has come under fire for not being too scientific. I'll see if I can dig up a link to that study.
One thing though - if you tested 450ppm for IO, then either your testing method was wrong, your test kit was bad, or you used tap water with high Ca
content in it to start with. IO should test around 340ppm or so, if I remember right. Oceanic will test around 450ppm or so. I use Reef Crystals, and it comes in around 360ppm.
Some salts will have high Ca
, but low alkalinity. Others will have low Ca
, but high alkalinity. Some will have low magnesium, others high. It really all depends. As I mentioned in a different thread just a few minutes ago, consistency is really more important. In my opinion, find a salt that you'll be able to buy consistently and learn how to work with it. I use Reef Crystals and would rather have higher Ca
content than it gives me. But I've learned how to correct it, and have no issues with my water parameters or stability, so why change? Find something that works for you, and stick with it.