B-Ionic

[MalHavoc]

As a side point, the "two part" additives have a side effect of raising your salinity over time. The additives are usually made of various chloride salts (as Christy mentioned) and also Sodium salts (like sodium bicarbonate, etc). The combination of this has the effect of raising the amount of sodium chloride in your tank. I've been using B-ionic in my tank for a few years now and while it works great, I have to watch my salinity as the months go by.