IO seems to be fine; I'm pretty sure they changed the formula after the humongous salt wars several years ago. I used to use either the aquacraft stuff or the bio-assay salt, but forget about finding it locally, and more recent testing sure seems to indicate that IO is as good as any of 'em. I add a little calcium chloride to bring the calcium to 400 and a little magnesium chloride to bring the magnesium to 1300 when I mix it up.