[Myka]

I prefer H2Ocean for my reef tanks, but I prefer IO for my fish only tanks. By your post I'm assuming you are asking which is the preferred salt for reef tanks, so I voted for H2Ocean.

I like H2Ocean for reef tanks because I only have to add magnesium and potassium, plus I prefer the lower (than IO) alkalinity so I can keep the alkalinity below 8 dKH in my reefs. It also mixes up much cleaner than IO which leaves a brown residue on the sides of the mixing barrel.

I like IO for fish only tanks because of the higher alkalinity and the cost.